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Full text of "Anatomy, descriptive and applied"

CoQege of S^tv^itiansi anti ^urgeonst 
TLibvaxv 




Digitized by tine Internet Arcliive 

in 2010 witli funding from 

Open Knowledge Commons (for the Medical Heritage Library project) 



http://www.archive.org/details/anatomydescriptOOgray 



ANATOMY 



DESCRIPTIVE AND APPLIED 



BY 

HENRY GRAY, F.R.S. 

FELLOW OF THE HOYAL COLLEGE OF SURGEONS; LECTUREB ON ANATOMY AT ST. GEORGE's 
HOSPITAL MEDICAL SCHOOL, LONDON 



A NEW AMERICAN EDITION 

THOROUGHLY REVISED AND RE-EDITED 
WITH THE ORDINARY TERMINOLOGY 



FOLLOA\'E» BY THE 



BASLE ANATOMICAL NOMENCLATURE IN LATIN 



BY 

EDWARD ANTHONY SPITZKA, M.D. 

DIRECTOR OF THE DANIEL. BAUGH INSTITUTE OF ANATOMY AND PROFESSOR OF GENERAL ANATOMY IN ' 
JEFFERSON MEDICAL COLLEGE, PHILADELPHIA 



HUustratet) witb 1225 lEnaravinos 




LEA & FEBIGER 

PHILADELPHIA AND NEW YORK 



Entered according to the Act of Congress, in the year 1913, by 

LEA & FEBIGER 
to the OfiB.ce of the Librarian of Congress. All rights reserved. 



THE FIRST EDITION OP THIS WORK 
WAS DEDICATED TO 

SIB BENJAMIN COLLINS BRODIE, Bart., F.R.S., D.C.L. 

IN ADMIRATION OF 

HIS GREAT TALENTS 

AND IN REMEMBRANCE OF 

MANY ACTS OF KINDNESS SHOWN TO THE ORIGINAL 

AUTHOR OF THE BOOK 

FROM AN 

EARLY PERIOD OF HIS PROFESSIONAL CAREER 



PREFACE. 



As a thoroughly practical treatise on the subject for the medical student, 
Gray's Anatomy, both in the original and its many succeeding editions, has long 
been held in the highest esteem. In this as in previous revisions the Editor has 
endeavored to adhere to the plan as much as possible, supplying such facts and 
views as the advances in the science of anatomy rendered it necessary to in- 
corporate. Descriptions of undue length have been curtailed, and any difficult 
passages in the text have been clarified; so that the essentials are here embodied 
into a fairly complete account of the structures of the human body and their 
development. It has also been the Editor's aim to achieve the utmost degree of 
uniformity in the mode of treatment throughout the work. 

Under the heading of Applied Anatomy many important medical and surgical 
considerations are discussed. In the use of descriptive terms, concerning which 
widely different opinions prevail, the Editor has sought to take a middle course, 
employing such designations as seem sanctioned by their usage in current medi- 
cal literature. The Basle Nomina A7iatomica Nomenclature, in italics, has been 
added in parentheses, except where the two nomenclatures are identical, and the 
terms are listed in the General Index. Here, also, they have been italicized, and 
thus distinguished they afford a working glossary of the BNA system. Other 
synonyms are printed in Roman type. 

Illustrations have been added from original drawings and preparations, and 
some from standard works, wherever it seemed that any important point could 
be made more clear. 

The Editor is greatly indebted to his assistants. Dr. Howard Dehoney, Demon- 
strator of Anatomy, and Dr. Henry E. Radasch, Assistant Professor of Histology 
and Embryology in the Jefferson Medical College, for valuable aid in the prepara- 
tion of this revision. The Editor also wishes to thank Mr. William A. Hassett, of 
Lea & Febiger, for indexing the book, for seeing it through the press, and for the 

valuable aid he has ungrudgingly given. 

E. A. S. 
Philadelphia, 1913. 



fv) 



PUBLISHERS' NOTE. 



Books, like men, have characters that can be analyzed- to a certain point, 
but beyond or below lies a quality, subtle as life, and incapable of analysis or 
imitation, which is called personality. The greater the author, and the more 
intense his mental action in creating his book, the more it partakes of this ele- 
ment. This principle, so clear as to be almost axiomatic, is illustrated to the 
fullest extent in the work in hand. Henry Gray combined two faculties, either 
one sufficient to make his name famous. He was a great anatomist and a great 
teacher. He possessed a thorough knowledge of anatomy and an equal insight 
into the best methods of imparting it to other minds. His text was unequalled 
in clearness, and he united with it a series of incomparable illustrations. He 
devised the method of engraving the names of the parts directly upon them, 
thereby exliibiting at a glance not only their nomenclature, but also their posi- 
tion, extent, and relations. His work, still unique in this respect, was also the 
first to employ colors. Summing all, it is hardly to be wondered at that students 
and teachers alike find their labors reduced and the permanence of knowledge 
increased by the use of such a book. 

On its original appearance, half a century ago, it immediately took the 
leading place, and it has not only maintained its position in its own subject, 
but has also become the best-known work in all medical literature in the 
English language. It is incomparably the greatest text-book in medicine, 
measured by the numbers of students who have used it, and it is unique also 
in being the one work which is certain to be carried from college to afi'ord 
guidance in the basic questions underlying practice. 

The consequent demand is evidenced in the number of editions, which 
collectively represent the labors of many of the leading anatomists since the 
early death of its talented author. In this new revision every line has been 
carefully considered, any possible obscurity has been clarified, the latest acces- 
sions to anatomical knowledge have been introduced, and much has been 
rewritten. Care has been exercised to make the text a homogeneous, sequen- 
tial, and complete presentation of the subject, sufficing for every need of the 
student, physician, or surgeon. 

As ample directions are given for dissecting, this volume will serve every 
requirement of the student throughout his course. The new nomenclature and 
that still in common use have been introduced in a manner rendering the work 
universal in the prime essential of terminology. The Table of Contents is so 
arranged as to give a complete conspectus of anatomy, a feature of ob^'ious 
value. The whole book is thoroughly organized in its headings and the 
sequence of subjects, so that the student receives his knowledge of the parts in 
their anatomical dependence. 

As a teaching instrument the new Gray's Anatomy embodies all that careful 
thought and unstinted expenditure can combine in book form. 

(vii) 



CONTENTS. 
DESCRIPTIVE AND APPLIED ANATOMY. 



OSTEOLOGY. 



Introduction 33 

General Anatomy of the Skeleton 

The Skeleton 35 

Number of the Bones 35 

Form of Bones 35 

Long Bones 35 

Short Bones 36 

Flat Bones 36 

Irregular Bones 36 

Surface of Bones 36 

Structure of Bone 38 

Bloodvessels of Bone 40 

Chemical Composition of Bone 41 

Ossification and Growth of Bone 42 

Applied Anatomy of the Bones 46 

SPECLA.L Anatomy of the Skeleton. 

The Vertebhal oh Spinal Column or the Spine. 

General Characters of a Vertebra. 

The Cervical VertebriB 49 

Atlas 50 

Axis : 52 

Seventh Cervical 53 

The Thoracic VertebrEe 53 

Peculiar Thoracic Vertebrce 54 

The Lumbar Vertebrae : ■ . . 56 

The Sacral and Coccygeal Vertebrae 58 

Sacrum 58 

The Sacral Canal 61 

Differences in the Sacrum of the 

Male and Female 61 

Coccyx 61 

Structure of the VertebrEe 62 

Development of the Vertebrae 63 

Development of the Atlas 63 

Development of the Axis 64 

Development of the Seventh Cervical , 64 

Development of the Lumbar Vertebrae .... 64 

The Vertebral Column as a Whole 66 

Surface Form of the Vertebral Column .... 67 

Applied Anatomy of the Vertebral Column. fi8 

The Skull. 

The Cerebral Cranium. 

The Occipital Bone 70 

The Parietal Bone 74 

The Frontal Bone 76 

Vertical Portion of the Frontal Bone. 76 
Horizontal or Orbital Portion of the 

Frontal Bone 79 

The Temporal Bone 80 

The Squamous Portion 80 

The Petromastoid Portion 81 

The Mastoid Portion 82 

The Petrous Portion 83 

The Tympanic Portion 87 



The Sphenoid Bone 89 

The Body of the Sphenoid Bone 90 

The Greater or Temporal Wings 92 

The Lesser or Orbital Wings 93 

The Pterygoid Processes 94 

The Sphenoidal Turbinated Processes. . 95 

The Ethmoid Bone 96 

The Horizontal Lamina or Cribriform 

Plate 96 

The Vertical Plate 97 

The Lateral Mass or Labyrinth 97 

The Bones of the Face. 

The Nasal Bones 99 

The Maxillae 100 

Changes Produced in the Upper Jaw by Age . 106 

The Lacrimal Bone 106 

The Malar Bone 107 

The Palate Bone 109 

The Turbinated Bone 113 

The Vomer 114 

The Mandible or Lower Jaw 115 

Changes Produced in the Mandible by 

Age 119 

Side Views of the Mandible at Different 

Periods of Life 119 

The Sutures 121 



The Skull 



Whole. 



The Vertex of the Skull 123 

The Base of the Skull 123 

The Lateral Region of the Skull 132 

The Temporal Fossa 132 

The Mastoid Portion 133 

The Zygomatic Fossa 133 

The Sphenomaxillary Fossa 134 

The Anterior Region of the Skull 134 

The Orbits 136 

The Nasal Cavity 138 

Development of the Skull 141 

Differences in the Skull Due to Age 143 

Obliteration of the Sutures 144 

Differences in the Skull Due to Sex 144 

Supernumerary, Wormian, Sutural or Epac- 

tal Bones 144 

Craniology 144 

Surface Form of the Skull 147 

Applied Anatomy of the Skull 149 



The Hyoid or Lingual Bone. 
The Thorax. 



153 



Boundaries of the Thorax 154 

The Cavity of the Thorax 1^7 

The Sternum or Breast Bone 157 

The Ribs 161 

Peculiar Ribs 163 

The Costal Cartilages 16o 

Surface Form of Thorax 166 

Applied Anatomy of Thorax 167 

(ix) 



CONTENTS 



The Upper Extremity. 

The Shoulder Girdle. 

The Clavicle 169 

Surface Form of the Clavicle 171 

Applied Anatomy of the Clavicie 172 

The Scapula or Shoulder Blade 172 

Surface Form of the Scapula 177 

Applied Anatomy of the Scapula 17S 



The Humerus or Arm Bone 178 

Surface Form of the Humerus 184 

Api^lied Anatomy of the Humerus 184 



The Forearm. 

The Ulna or Elbow Bone 185 

Surface Form of the Ulna . 190 

The Radius 190 

Surface Form of the Radius 192 

Applied Anatomy of the Radius and 

Ulna 192 

The Hand. 

The Carpus 195 

Bones of the Upper Row 196 

The Scaphoid or Navicular Bone.. 196 

The Semilunar Bone 197 

The Cuneiform Bone 197 

The Pisiform Bone 198 

Bones of the Lower Row 198 

The Trapezium 198 

The Trapezoid 199 

The Os Magnum 199 

The Unciform 200 

The Metacarpus 201 

Peculiar Characters of the Metacarpal 

Bones 202 

The Phalanges of the Hand 204 

Surface Form of the Bones of the Hand .... 205 

Applied Anatomy of the Bones of the Hand 205 

Development of the Bones of the Hand .... 206 



The Lower Extremity. 

The Os Innominatum 207 

The Ilium 207 

The Ischium 210 

The Pubis 212 

The Cotyloid Cavity or Acetabulum.. . 213 

The Obturator or Thyroid Foramen . . . 213 

The Pelvis 215 

Position of the Pelvis 217 

Axes of the Pelvis 218 

Differences between the Male and 

Female Pelvis 218 

Surface Form of the Pelvis 219 

Applied Anatomy of the Pelvis 220 

The Thigh. 

The Femur or Thigh Bone 221 

Surface Form of the Femur 228 

Applied Anatomy of the Femur 229 

The Leg. 

The Patella or Knee Cap 230 

Surface Form of the Patella 231 

Applied Anatomy of the Patella 231 

The Tibia or Shin Bone 231 

Surface Form of the Tibia 236 

The Fibula or Calf Bone 236 

Surface Form of the Fibula 238 

Applied Anatomy of the Bones of the Leg. . 239 

The Foot: 

The Tarsus 239 

The Calcaneus 239 

The Astragalus or Ankle Bone 244 

The Cuboid 245 

The Scaphoid or Navicular Bone 246 

The Cuneiform or Wedge Bones 247 

The Metatarsal Bones 249 

Peculiar Characters of the Metatarsal 

Bones 250' 

The Phalanges of the Foot 252 

Development of the Foot 254 

Construction of the Foot as a Whole 254 

Surface Form of the Foot 255 

Applied Anatomy of the Foot 256 

Sesamoid Bones 257 



THE AETICULATIONS OR JOINTS. 



structures Composing the Joints 259 

Bone 259 

Cartilage 259 

Ligaments 261 

Synovial Membrane 261 

Forms of Articulation : 

Synarthrosis (Immovable Articulation) 263 

Amphiarthrosis (Mixed Articulation) . . 264 

Diarthrosis (Movable Articulation) .... 264 

Kinds of Movement Admitted in Joints. . . . 266 

Ligamentous Action of Muscles 267 

Articulations of the Trunk. 

Articulations of the Vertebral Column 268 

The Ligaments of the Vertebral Bodies 

or Centra 268 

The Ligaments Connecting the Laminae 271 
The Ligaments Connecting the Articu- 
lar Processes 271 

The Ligaments Connecting the Spinous 

Processes 272 

The Ligaments Connecting the Trans- 
verse Processes 272 

Articulations of the Atlas with Axis 273 

Articulations of the Vertebral Column with Cranium-. 

Articulation of Atlas with Occipital Bone. . 275 

Articulation of Axis with Occipital Bone . . . 277 
Applied Anatomy of Articulations of the 

Vertebral Column 278 



The Temporomandibular Articulation 279 

Surface Form 281 

Applied Anatomy 281 

Articulations of the Ribs with the Vertebral 

or the Costovertebral Articulations . . 282 

The Costocentral Articulations 282 

The Costotransverse Articulations 284 

The Costosternal Articulations 286 

Articulations of the Cartilages of the 

Ribs with Each Other 288 

Articulations of the Ribs with their 

Cartilages 288 

Articulations of the Sternum 288 

Articulation of the Vertebral Column with 

the Pelvis ■ 289 

Articulations of the Pelvis 290 

Articulation of the Sacrum and Ilium . . 290 
Ligaments Passing between the Sacrum 

and Ischium 291 

Articulation of the Sacrum and Coc- 
cyx 292 

Articulation of the Pubic Bones 294 

Articulations of the Upper Extremity. 

Sternocla-vdcular Articulation 295 

Surface Form , 297 

Applied Anatomy 297 

Acromioclavicular Articulation or Scapulo- 
clavicular Articulation 297 

Surface Form 299 

Applied Anatomy 299 



CONTENTS 



XI 



Proper Ligaments of the Scapula 299 

The Shoulder-joint 301 

Surface Form 304 

Applied Anatomy 304 

The Elbow-joint 306 

Surface Form 309 

Applied Anatomy 309 

Radio-ulnar Articulation 310 

Superior Artirulation 310 

Surf:H-r I-(,nii 311 

AiU'lii''! Anatomy 311 

Middle Kadio-ulnar Ligaments 311 

Inferior Articulation 312 

Surface Form 314 

The Radiocarpal or Wrist-joint 314 

Surface Form 315 

Applied Anatomy 315 

Articulations of the Carpus 315 

Articulations of the First Row of Carpal 

Bones 315 

Articulations of the Second Row of 

Carpal Bones '. . 316 

Articulations of the Two Rows of 

Carpal Bones with Each Other 316 

Carpometacarpal Articulations 317 

Articulation of the Metacarpal Bone 

of the Thumb with the Trapezium. . 317 
Articulations of the Metacarpal Bones 
of the Four Inner Fingers with the 

Carpus 318 

Articulations of the Metacarpal Bones 

with Each Other 319 

Metacarpophalangeal Articulations 320 

Surface Form. 321 

Articulations of the Phalanges 321 

Articulations of the Lower Extremity. 

The Hip-joint 322 

Surface Form 329 



The Hip-joint — 

Applied Anatomy 329 

The Knee-joint 331 

Surface Form 33y 

Applied Anatomy 338 

Tibiofibular Articulation 340 

Superior Tibiofibular Articulation 340 

Middle Tibiofibular Ligament or Inter- 
osseous Membrane 341 

Inferior Tibiofibular Articulation 341 

The Tibiotarsal Articulation or Ankle-joint 342 

Surface Form of Ankle-joint 346 

Applied Anatomy of Ankle-joint 346 

Articulations of the Tarsus 347 

Articulation of the Calcaneus and 

Astragalus 347 

Articulation of the Calcaneus with the 

Cuboid 347 

The Ligaments Conneoting the Cal- 
caneus and Scaphoid 348 

Applied Anatomy 349 

Articulation of the Astragalus with 

the Scaphoid Bone 349 

The Articulation of the Scaphoid with 

the Cuneiform Bones 349 

The Articulation of the Scaphoid with 

the Cuboid 350 

The Articulations of the Cuneiform 
Bones with Each Other or the Inter- 
cuneiform Articulations 350 

The Articulation of the External 

Cuneiform Bone with the Cuboid 351 

Applied Anatomy •. 351 

Tarsometatarsal Articulations 351 

Articulations of the Metatarsal Bones 

with Each Other 352 

Metatarsophalangeal Articulations 353 

Articulations of the Phalanges 354 

Surface Form 354 

Applied Anatomy 364 



THE MUSCLES AND FASCIA. 



General Description of Muscles 355 

Form and Attachment of Muscles 357 

Applied Anatomy of Muscles 359 

General Description of Tendons 360 

General Description of Aponeurosis 360 

General Description of Fasciae 360 

Development of Skeletal Musculature 361 

Muscles and Fascia of the Cranium and Face. 

Subdivision in Groups 362 

The Cranial Region 362 

The Skin of the Scalp 363 

Superficial Fascia 363 

The Occipitofrontalis 36.3 

Applied Anatomy 365 

The Auricular Region '. 365 

Attrahens Aurem 366 

Attolens Aurem 366 

Retrahens Aurem 366 

The Palpebral Region 366 

Orbicularis Palpebrarum 366 

Corrugator Supercilii 367 

Tensor Tarsi or Horner's Muscle 367 

Tlie Orbital Region 368 

Orbital Septum 368 

Levator Palpebrae Superioris 369 

Recti 370 

Superior Oblique 370 

Inferior Oblique 370 

Fasciae of the Orbit 371 

Applied Anatomy 371 

The Nasal Region 372 

Py ramidalis Nasi 372 

Levator Labii Superioris Alaeque Nasi . 372 

Dilator Naris Posterior 372 

Dilator Naris Anterior 372 

Compressor Naris 372 

Compressor Narium Minor 372 

Depressor Alae Nasi 372 



The Maxillary Region 373 

Levator Labii Superioris 373 

Levator Anguli Oris 373 

Zygomaticus Major 373 

Zygomaticus Minor 373 

The Mandibular Region 374 

Levator Menti 374 

Depressor Labii Inferioris or Quad- 

ratus Menti 374 

Depressor Anguli Oris 374 

The Buccal Region 374 

Orbicularis Oris 374 

Buccinator 375 

Risorius 377 

The Temporomandibular Region 377 

Masseteric Fascia 377 

Masseter Muscle 377 

Temporal Fascia 378 

Temporal Muscle 378 

The Pterygomandibular Region 379 

External Pterygoid Muscle 379 

Internal Pterygoid Muscle 380 

Surface Form of Muscles of Head and Face. 381 

Muscles and Fascia of the Neck. 

Subdivisions into Groups 381 

The Superficial Cer\'ical Region 381 

Superficial Cervical Fascia 381 

Platysma 381 

Deep Cervical Fascia 382 

Applied Anatomy 384 

Sternomastoid 385 

Triangles of the Neck 386 

Applied Anatomy 386 

The Infrahyoid Region 386 

Sternohyoid 386 

Sternothyroid 387 

Thyrohyoid 387 

Omohyoid 3SS 



CONTENTS 



The Suprahyoid Region 388 

Digastric 388 

Stylohyoid 389 

Mylohyoid 389 

Geniohyoid 390 

The Lingual Region 391 

Geniohyoglossus 391 

Hyoglossus 391 

Chondroglossus 392 

Styloglossus 392 

The Muscle Substance of the Tongue. . 393 

Applied Anatomy 394 

The Pharyngeal Region 394 

Inferior Constrictor 394 

Middle Constrictor 395 

Superior Constrictor 395 

Stylopharyngeus 396 

The Palatal Region 397 

Levator Palati 397 

Tensor Palati 397 

Palatal Aponeurosis 397 

Azygos Uvulae 398 

Palatoglossus 398 

Palatopharyngeus 398 

Salpingopharyngeus 399 

Applied Anatomy 399 

The Anterior Vertebral Region 400 

Rectus Capitis Anticus Major 400 

Rectus Capitis Anticus Minor 400 

Rectus Capitis Lateralis 400 

Longus Colli 401 

The Lateral Vertebral Region 401 

Scalenus Anticus 401 

Scalenus Medius 401 

Scalenus Posticus 402 

Surface Form of Muscles of Neck 402 

Muscles and Fascia of the Trtjnk. 

Subdivision into Groups 403 

Muscles of the Back. 

Subdivision into Groups 403 

The First Layer 404 

Superficial Fascia 404 

Deep Fascia 404 

Trapezius 404 

Ligamentum Nuchae 406 

Latissimus Dorsi 406 

The Second Layer 407 

Levator Anguli Scapulae 407 

Rhomboideus Minor 407 

Rhomboideus Major 407 

The Third Layer 408 

Serratus Posticus Superior 408 

Serratus Posticus Inferior 408 

Vertebral Aponeurosis 408 

Splenius Capitis 409 

Splenius Colli 409 

The Fourth Layer 410 

Erector Spinae 410 

Iliocostalis 410 

Musculus Accessorius 410 

Cervicalis Ascendens 412 

Longissimus Dorsi 412 

Trans versalis Cervicis 412 

Trachelomastoid 412 

Spinalis Dorsi ." 412 

Spinalis Colli 412 

Complexus 412 

The Fifth Layer 413 

Semispinalis Dorsi 413 

Semispinalis Colli 413 

Multifidus Spinae 413 

Rotatores Spinae 413 

Supraspinales 414 

Interspinales 414 

Extensor Coccygis 414 

Intertransversales 414 

Rectus Capitis Posticus Major 414 

Rectus Capitis Posticus Minor 414 

Obliquus Inferior 415 

Obliquus Superior 415 

Suboccipital Triangle 415 

Applied Anatomy 416 



Muscles and Fascice of the Thorax. 

Intercostal Fascia 417 

Intercostal Muscles 417 

External Intercostals 417 

Internal Intercostals 417 

Infracostales 417 

Triangularis Sterni 417 

Levatores Costarum 417 

Diaphragm 418 

Muscles of the Abdomen. 

Antero-lateral Muscles of the Abdomen . . . 423 

Superficial Fascia 424 

Deep Fascia 424 

External or Descending Oblique 424 

Aponeurosis of the External 

Oblique 425 

External Abdominal Ring 426 

Applied Anatomy 427 

Poupart's Ligament 427 

Gimbernat's Ligament 428 

Triangular Fascia 428 

Ligament of Cooper 428 

Internal or Ascending Oblique 428 

Cremaster Muscle 430 

Transversalis 432 

Rectus Abdominis 433 

Pyramidalis 435 

Linea Alba 435 

Linea Semilunares 436 

Fascia Transversalis 436 

Internal or Deep Abdominal Ring 437 

Inguinal or Spermatic Canal 437 

Surface Form 439 

Posterior Muscles of the Abdomen 439 

The Fascia Covering the Quadratus 

Lumborum 439 

Quadratus Lumborum 439 

Muscles and Fascice of the Pelvic Outlet 

The Central Tendinous Point of the 

Perineum 442 

The Muscles of the Perineum in the Male. . 442 

Superficial Transverse Perineal 442 

Accelerator Urinae 443 

Erector Penis 444 

The Muscles of the Perineum in the Female 445 

Superficial Transverse Perineal.. ....... 445 

Sphincter Vaginae 445 

Erector Clitoridis 446 

The Triangular Ligament in the Male and in 

the Female 446 

Compressor or Constrictor Urethrae. . . 448 

The Pelvic Fascia 448 

Levator Ani 450 

Coccygeus 453 

Muscles of the Ischiorectal Region 453 

Corrugator Cutis Ani 453 

External Sphincter Ani 453 

Internal Sphincter Ani 454 

Ischiorectal Fossa 454 



Muscles and Fascia of the Upper Extremity. 

Subdivision into Groups 455 

Dissection of Pectoral Region and Axilla . . . 455 

Muscles and Fascice of the Thoracic Region. 

The Anterior Thoracic Region 455 

Superficial Fascia 455 

Deep Fascia 456 

Pectoralis Major 456 

Costocoracoid Membrane or the Clavi- 

pectoral Fascia 459 

Pectoralis Minor 460 

Subclavius 460 

The Lateral Thoracic Region 461 

Serratus Magnus 461 

Applied Anatomy 461 



CONTENTS 



Muscles and Fascim of the Shoulder and Arm. 

The Acromial Region 462 

Deltoid 462 

Applied Anatomy 463 

The Anterior Scapular Region 463 

Subscapularis 464 

The Posterior Scapular Region 464 

Supraspinatus 464 

Infraspinatus 465 

Teres Minor 466 

Teres Major 466 

Muscles and Fascice of the Arm, 

The Anterior Humeral Region 467 

Deep Fascia 467 

Coracobrachialis 468 

Biceps or Biceps Flexor Cubiti 469 

Brachialis Anticus 469 

The Posterior Humeral Region 470 

Triceps or Triceps Extensor Cubiti .... 470 

Subanconeus 471 

Muscles and Fascice of the Forearm. 

Deep Fascia 471 

The Anterior Radioulnar Region 472 

Superficial Layer 472 

Pronator Teres 472 

Applied Anatomy . . . '. 473 

Flexor Carpi Radialis 473 

Palmaris Longus 474 

Flexor Carpi Ulnaris 474 

Flexor Sublimis Digitorum 475 

Deep Layer 476 

Flexor Profundus Digitorum 476 

Flexor Longus PoUicis 476 

Pronator Quadratus 478 

Applied Anatomy 478 

The Radial Region 479 

Brachioradialis 479 

Extensor Carpi RadiaUs Longior 479 

Extensor Carpi Radialis Brevior 479 

The Posterior Radioulnar Region 480 

Superficial Layer 480 

Extensor Communis Digitorum . . . 480 

Extensor Minimi Digiti 481 

Extensor Carpi Ulnaris 482 

Anconeus 482 

Supinator (Brevis) 482 

Extensor Ossis Metacarpi PoUicis. 482 

Extensor Brevis PoUicis 483 

Extensor Longus PoUicis 484 

Extensor Indicis 484 

Applied Anatomy 485 

Muscles and Fascice of the Hand. 

Anterior Annular Ligament 486 

The Synovial Membranes of the Flexor 

Tendons at Wrist 486 

Applied Anatomy 487 

Bursae about the Hand and Wrist 487 

Posterior Annular Ligament 487 

Superficial Transverse Ligament of Fingers . 489 

The Radial Region 489 

Abductor PoUicis 489 

Opponens PoUicis 490 

Flexor Brevis PoUicis ,. . . . 490 

Adductor Obliquus PoUicis 490 

Adductor Transversus PoUicis 492 

The Ulnar Region 492 

Palmaris Brevis 492 

Abductor Minimi Digiti 492 

Flexor Brevis Minimi Digiti 493 

Opponens Minimi Digiti 493 

The Middle Palmar Region 493 

Lumbricales 493 

Interossei 493 

Dorsal Interossei 494 

First Dorsal Interossei Muscle or 

Abductor Indicis 494 

Palmar Interossei 494 



Surface Form of Muscles of the Upper Ex- 
tremity 495 

Applied Anatomy of Muscles of the Upper 
Extremity 497 



Muscles and Fasci/E of the Lower Extremity. 

Subdivision into Groups 501 

Muscles and Fascice of the Iliac Region. 

lUac Fascia 502 

Psoas Magnus 504 

Psoas Parvus 504 

Iliacus 504 

Applied Anatomy 505 

Muscles and Fasciw of the Thigh. 

The Anterior Femoral Region 505 

Superficial Fascia 506 

Deep Fascia or Fascia Lata 506 

Applied Anatomy 508 

Tensor Fasciae Femoris 508 

Sartorius 508 

Quadriceps Extensor 509 

Rectus Femoris 510 

Vastus Externus 510 

Vastus Internus 510 

Crureus 511 

Subcrureus 512 

AppUed Anatomy 512 

The Internal Femoral Region 512 

Gracilis 512 

Pectineus 513 

Adductor Longus 513 

Adductor Brevis 514 

Adductor Magnus 514 

Hunter's Canal 515 

Applied Anatomy 515 

The Muscles and Fascice of the Hip. 

The Gluteal Region 515 

Gluteus Maximus 515 

Gluteus Medius 516 

Gluteus Minimus 517 

Pyriformis 517 

Obturator Membrane 517 

Obturator Internus 518 

GemelU 520 

Quadratus Femoris 520 

Obturator Externus 521 

The Posterior Femoral Region 522 

Biceps Femoris 522 

Semitendinous 524 

Semimembranous 524 

Applied Anatomy 525 

Muscles and Fascice of the Leg. 

The Anterior Tibiofibular Region 525 

Deep Fascia of the Leg 525 

Tibialis Anticus 526 

Extensor Proprius Hallucis 527 

Extensor Longus Digitorum 527 

Peroneus Tertius 527 

The Posterior Tibiofibular Region 528 

Superficial Layer 528 

Gastrocnemius 528 

Soleus 529 

Tendo Achillis 530 

Plantaris 530 

Deep Layer 531 

Deep Transverse Fascia 531 

Popliteus 531 

Flexor Longus Hallucis 532 

Flexor Longus Digitorum 533 

Tibialis Posticus 533 

The Fibular Region 534 

Peroneus Longus 534 

Peroneus Brevis 535 

Applied Anatomy 535 



CONTENTS 



Muscles and Fascice of the Foot. 

Anterior Annular Ligament 536 

Internal Annular Ligament 536 

External Annular Ligament 537 

The Dorsal Region 537 

Fascia of the Dorsal Region 537 

Extensor Brevis Digitorum 537 

The Plantar Region 537 

Plantar Fascia 537 

The First Layer 538 

Abductor Hallucis 538 

Flexor Brevis Digitorum 538 

Fibrous Sheaths of Flexor Tendons 539 

Abductor Minimi Digiti 539 



The Plantar Region — 

The Second Layer 539 

Flexor Accessorius 539 

Lumbricales 540 

The Third Layer 541 

Flexor Brevis Hallucis 541 

Adductor Obliquus Hallucis 541 

Adductor Transversus Hallucis . . . 541 

Flexor Brevis Minimi Digiti 541 

The Fourth Layer 541 

Interossei Muscles 541 

Surface Form of Muscles of the Lower 

Extremity. 543 

Applied Anatomy of Muscles of the Lower 

Extremity 544 



THE VASCULAR SYSTEMS. 



The Heart and Bloodvessels. 
The Circulation of the Blood 



The Pericardium. 

Structure of the Pericardium 

Vestigial Fold of the Pericardium 

Applied Anatomy of the Pericardium. 

The Heart. 

Position of the Heart 

Component Parts of the Heart 

The Cavities of the Heart 

Right Auricle ". . . . 

Right Ventricle 

Left Auricle . 



548 
550 
550 



551 
553 
553 
554 
557 
559 



The Cavities of the Heart — 

Left Ventricle 560 

Capacity of the Cavities of the Heart 561 

Size and Weight of the Heart 562 

Structure of the Heart 562 

Endocardium 562 

Myocardium 562 

Fibres of Auricles 562 

Fibres of Ventricles 563 

The Cardiac Cycle and the Action of the 

Valves 565 

Surface Form of the Heart 567 

Applied Anatomy of the Heart 568 

Peculiarities of the Vascular System in the 

Fetus 568 

Fetal Circulation 570 

Changes in the Vascular System at Birth . . 571 



THE ARTEEIES. 



The Distribution of the Arteries 572 

Anastomosis of the Arteries 572 

Histology of Arteries and Capillaries 573 

Bloodvessels of the Bloodvessel Wall 573 

Lymphatics of the Arteries 574 

Nerves of the Arteries 574 

Arterial Sheath 574 

Applied Anatomy of the Arteries 574 

The Pulmonary Artery. 

Right Branch of the Pulmonary Artery. . . . 575 

Left Branch of the Pulmonary Artery 575 

Applied Anatomy of the Pulmonary Artery 575 

The Aorta. 

The Ascending Aorta. 

Relations of the Ascending Aorta 576 

Branches of the Ascending Aorta 578 

The Coronary Arteries 578 

Applied Anatomy of the Coronary 

Arteries 578 



The Arch of the Aorta. 

Relations of the Arch of the Aorta 

Peculiarities of the Arch of the Aorta 

AppHed Anatomy of the Arch of the Aorta . 

Branches of the Arch of the Aorta 

The Innominate Artery 

Relations 

Branches 

Thyroidea Ima 

Applied Anatomy 

Peculiarities 



579 
580 
580 
581 
582 
582 
582 
582 
582 
583 



The Arteries of the Head and Neck. 

The Common Carotid Artery. 

Relations of the Common Carotid Artery. . 583 

Peculiarities of the Common Carotid Artery 586 

Surface Marking of the Common Carotid 

Artery 586 

Applied Anatomy of the Common Carotid 

Artery 586 



The External Carotid Artery 

Relations 

Surface Marking 

Applied Anatomy 

Branches 

Superior Thyroid Artery 

Applied Anatomy 

Lingual Artery 

Applied Anatomy 

Facial Artery 

Applied Anatomy 

Occipital Artery 

Posterior Auricular Artery 

Ascending Pharyngeal Artery. . . . 

Applied Anatomy 

Superficial Temporal Artery 

Applied Anatomy 

Internal Maxillary Artery 

Applied Anatomy 

The Triangles of the Neck 

Anterior Triangle of the Neck 

Posterior Triangle of the Neck 

The Internal Carotid Artery 

Cervical Portion . 

Petrous Portion 

Cavernous Portion 

Cerebral Portion 

Peculiarities 

Applied Anatomy 

Branches 

Tympanic 

Vidian 

Arteriae Receptaculi 

Anterior Meningeal 

Ophthalmic 

Anterior Cerebral 

Middle Cerebral 

Posterior Communicating Artery. 
Choroid Artery 



The Arteries of the Brain. 

The Central GangUonic System 

The Cortical Arterial System 

The Vertebral Artery 

Applied Anatomy 



588 
588 
588 
589 
589 
590 
590 
591 
592 
595 
595 
596 
597 
597 
597 
598 
598 
600 
602 
603 
605 
606 
607 
607 



609 
609 
609 
610 
614 
616 
617 
617 



618 
619 
619 
620 



CONTENTS 



The Ahteries of the Upper Extremity. 

The Subclavian Artery. 

First Part of the Right Subclavian Artery . . 623 

First Part of the Left Subclavian Artery . . . 625 
Second and Third Parts of the Subclavian 

Artery 625 

Peculiarities of the Subclavian Artery 626 

Surface Marking of the Subclavian Artery . . 626 

Applied Anatomy of the Subclavian Artery . 627 

Branches 628 

Vertebral Artery 628 

Thyroid Axis 628 

Peculiarities 630 

Internal Mammary Artery 631 

Superior Intercostal Artery 633 

The Axilla. 

Boundaries of the Axilla 633 

Contents of the Axilla 634 

Applied Anatomy 634 

The Axillary Artery 635 

Surface Marking 637 

Applied Anatomy 637 

Branches 638 

Superior Thoracic 638 

Acromiothoracic 638 

Long Thoracic or External Mam- 
mary 638 

Alar Thoracic 639 

Subscapular 639 

Circumflex Arteries 639 

The Brachial Artery. 

Relations of the Brachial Artery 640 

Anatomy of the Bend of the Elbow 641 

Peculiarities of the Brachial Artery 641 

Surface Marking of the Brachial Artery. . . . 641 

Applied Anatomy of the Brachial Artery. . . 641 

Branches of the Brachial Artery 642 

Superior Profunda Artery 642 

Nutrient Artery 643 

Inferior Profunda Artery 643 

Anastomotica Magna 643 

Muscular Branches 644 

The Anastomosis Around the Elbow- 
joint 644 

The Radial Artery 644 

The Deep Palmar Arch 645 

Surface Marking 646 

Applied Anatomy 646 

Branches 646 

Radial Recurrent 646 

Muscular Branches 646 

Anterior Radial Carpal 647 

Superficialis Volae 647 

Posterior Radial Carpal 647 

Dorsalis Pollicis. 647 

Dorsalis Indicis 647 

Princeps Pollicis 647 

Radialis Indicis ; 647 

Perforating Arteries 648 

Palmar Interosseous 648 

Palmar Recurrent Branches 648 

The Ulnar Artery 648 

Surface Marking 649 

Applied Anatomy 649 

Branches 650 

Anterior Ulnar Recurrent 650 

Posterior Ulnar Recurrent 650 

Interosseous Artery 650 

Muscular Branches 651 

Anterior Ulnar Carpal 651 

Posterior Ulnar Carpal 651 

Profunda Branch 651 

Superficial Palmar Arch 652 

Surface Marking 652 

Applied Anatomy 652 

The Arteries of the Trunk. 
The Descending Aorta. 

The Thoracic Aorta 653 

Applied Anatomy 654 

Branches 654 



The Thoracic Aorta — Branches — 

Bronchial .VrtiTJfs 654 

CEso|.h:ii;(M! ,\riiTies 654 

Peric;ir.li;il \il-rirs 654 

MediiisliiKil I'.iaiiches 654 

Intercostal Arteries 655 

Applied Anatomy 657 

The Abdominal Aorta 657 

Surface Marking 657 

Applied Anatomy 658 

Branches 658 

Inferior Phrenic Arteries 658 

The Cceliac Axis or Artery 659 

Applied Anatomy 662 

The Suprarenal Artery 662 

The Lumbar Arteries 662 

The Superior Mesenteric Artery... 663 

The Renal Arteries 665 

The Spermatic Arteries 665 

The Ovarian Arteries 665 

The Inferior Mesenteric Artery . . . 666 

The Cojntnon Iliac Arteries. 

Relations of the Common Iliac Arteries. . . . 668 

Branches of the Common Iliac Arteries .... 668 

Peculiarities of the Common Iliac Arteries . 668. 

Surface Marking 669 

Applied Anatomy of the Common Iliac 

Arteries 669 

The Internal Iliac Artery 669 

Applied Anatomy 671 

Branches 671 

Superior Vesical 671 

Middle Vesical 672 

Inferior Vesical 672 

Middle Hemorrhoidal 672 

Uterine Artery 672 

Vaginal Artery 672 

Applied Anatomy 673 

Obturator Artery 673 

Internal Pudic Artery 674 

Sciatic Artery 677 

Iliolumbar Artery 678 

Lateral Sacral Arteries 678 

Gluteal Artery 678 

Surface Marking 679 

Applied Anatomy 679 

The External Iliac Artery 679 

Surface Marking 680 

Applied Anatomy 680 

Branches 680 

Deep Epigastric Artery 680 

Applied Anatomy 681 

Deep Circumflex Iliac Artery 682 

The Arteries of the Lower Extremity. 

The Femoral Artery. 

The Femoral or Crural Sheath 683 

The Femoral or Crural Canal 684 

Scarpa's Triangle 685 

Hunter's Canal or the Adductor Canal 685 

Relations of the Femoral Artery 686 

PecuUarities of the Femoral Artery 687 

Surface Marking of the Femoral Artery .... 687 

Applied Anatomy of the Femoral Artery. . . 687 

Branches of the Femoral Artery 688 

Superficial Epigastric ' 689 

Superficial Circumflex Iliac 689 

Superficial External Pudie.or the Supe- 
rior Superficial External Pudic 689 

Deep External Pudic 689 

Muscular Branches 6S9 

Deep Femoral or the Profunda Femoris 689 

The Popliteal Artery. 

The Popliteal Space 691 

Boundaries 692 

Contents 692 

Position of Contained Parts 692 

Peculiarities 693 

Surface Marking 693 

Applied Anatomy 693 

Branches 694 



CONTENTS 



The Popliteal Space — Branches — 

Superior Muscular Branches 694 

Inferior Muscular or Sural 

Branches 694 

Cutaneous Branches 694 

Superior Articular Arteries 694 

Azygos Articular Artery 695 

Inferior Articular Arteries 695 

Circumpatellar Anastomosis 696 

The Anterior Tibial Artery 696 

Surface Marking 697 

Applied Anatomy 697 

Branches 697 

Posterior Recurrent Tibial 698 

Superior Fibular 698 

Anterior Recurrent Tibial 698 

Muscular Branches 698 

The Dorsalis Pedis Artery 698 

Surface Marking 699 

Applied Anatomy 699 

Branches 699 



The Dorsalis Pedis Artery — Branches — 

Cutaneous Branches 699 

Tarsal Artery 699 

Metatarsal Artery 699 

Communicating Artery 700 

The Posterior Tibial Artery. 700 

Surface Marking 701 

Applied Anatomy 701 

Branches 701 

Peroneal Artery 701 

Cutaneous Branches 702 

Nutrient Artery 702 

Muscular Branches 703 

Communicating Branch 703 

Malleolar or Internal Malleolar. . . 703 

Internal Calcaneal 703 

Internal Plantar Artery 703 

External Plantar Artery 703 

Surface Marking 704 

Apphed Anatomy 704 



THE A^EINS. 



Subdivisions of the Veins 705 

Histology of the Veins 706 

Superficial or Cutaneous Veins 707 

Deep Veins 707 

Sinuses 707 

The Pulmonary Veins. 
Applied Anatomy of the Pulmonary Veins . . 708 

The Systemic Veins. 
The Cardiac Veins. 
The Coronary Sinus 



708 



The Veins of the Head and Neck. 

Veins of the Exterior of the Head and Face 710 

Frontal Vein 710 

Supraorbital Vein 710 

Angular Vein 710 

Facial Vein 710 

Common Facial Vein 710 

Applied Anatomy 711 

Superficial Temporal Vein 712 

Pterygoid Plexus 712 

Internal Maxillary Vein 712 

Temporomaxillary Vein 712 

Posterior Auricular Vein 712 

Occipital Vein 713 

The Veins of the Neck 713 

External Jugular Vein 713 

Posterior External Jugular Vein 713 

Anterior Jugular Vein 713 

Internal Jugular Vein 714 

Applied Anatomy 717 

Vertebral Vein 717 

The Veins of the Diploe 718 

Meningeal or Dural Veins 719 

The Cerebral Veins _ V19 

Superficial Cerebral Veins 719 

Deep Cerebral Veins or Veins of Galen 720 

Superficial Cerebellar Veins 720 

Deep Cerebellar Veins 720 

Veins of the Pons 720 

Veins of the Medulla Oblongata 721 

The Sinuses of the Dura. Ophthalmic Veins 

and Emissary Veins 721 

Superior Sagittal Sinus 721 

Inferior Sagittal Sinus 722 

Straight or Tentorial Sinus 722 

Lateral Sinuses 722 

Occipital Sinus 723 

Cavernous Sinus 724 

Applied Anatomy 724 

Sphenoparietal Sinuses 725 

Circular Sinus 726 

Superior Petrosal Sinus 726 



The Sinuses of the Dura. Ophthalmic Veins 
and Emissary Veins — 

Inferior Petrosal Sinus 726 

Transverse or Basilar Sinus 727 

Emissary Veins 727 

Applied Anatomy 727 



The Veins of the Upper Extremity and Thorax. 

The Superficial Veins of the Upper Ex- 
tremity 728 

Superficial Veins of the Hand and 

Fingers 728 

Anterior Ulnar Vein 729 

Posterior Ulnar Vein 729 

Common Ulnar Vein 729 

Radial Vein 730 

Median Vein 730 

BasUic Vein 730 

Cephalic Vein 730 

The Deep Veins of the Upper Extremity. . . 731 

Interosseous Veins 731 

Deep Palmar Veins 731 

Brachial Veins 731 

Axillary Vein 731 

Applied Anatomy 732 

Subclavian Vein 732 

Innominate or Brachiocephalic Veins . . 733 

Internal Mammary Veins 734 

Vertebral Vein 734 

Inferior Thyroid Veins 734 

Superior Intercostal Veins 735 

Superior Vena Cava 735 

Azygos Veins 736 

Applied Anatomy 737 

Bronchial Veins 737 

The Vertebral Veins 737 

Extravertebral Veins 737 

Intravertebral Veins 738 

Veins of the Bodies of the Vertebrae . . . 738 

Veins of the Spinal Cord 739 



Veins of the Lower Extremity, Abdomen, and j 

Superficial Veins of the Lower Extremity ... 739 

Superficial Veins of the Foot 739 

Internal or Long Saphenous Vein 740 

External or Short Saphenous Vein 741 

Applied Anatomy 741 

Deep Veins of the Lower Extremity 741 

Deep Veins of the Foot 741 

Posterior Tibial Veins 742 

Anterior Tibial Veins 742 

Pophteal Vein 742 

Femoral Vein 742 

External Iliac Vein 742 

Deep Epigastric Vein 742 

Deep Circumflex Iliac Vein 742 



CONTENTS 



XVII 



Deej) Veins of the Lower Extremity — 

Pubic Vein 743 

Internal Iliac Vein 743 

Hemorrhoidal Plexus 745 

. Vesicoprostatic Plexus 745 

Vesical Plexus 745 

Applied Anatomy 745 

Dorsal Veins of the Penis 746 

Vaginal Plexuses and Veins 747 

Uterine Plexuses 747 

Common Iliac Veins 747 

Inferior Vena Cava 748 

Applied Anatomy 748 

Lumbar Veins 749 

Spermatic Veins 750 

Applied Anatomy 750 

Ovarian Veins 751 



Deep Veins of the Lower Extremity — 

Renal Veins 751 

Suprarenal Veins 751 

Inferior Phrenic Veins 751 

Hepatic Veins 751 

The Portal System of Vkins. 

The Portal Vein 751 

The Splenic Vein 752 

The Superior Mesenteric Vein 753 

The Cysrie Vein 754 

Paraumbilical Veins 754 

Anastomosis between Portal and Systemic 

Veins 754 

Applied Anatomy 754 

Development of the Blood-vascular System . 755 



THE LYMPHATIC SYSTEM. 



Subdi\asions into Superficial and Deep Sets . 767 

Lymph Nodes or Lymphatic Glands 768 

Hemolymph Nodes 768 

Structure of Lymphatics 769 

Origin of Lymphatics 769 

Termination of Lymphatics 769 

Development of Lymphatic Vessels 769 

Applied Anatomy 770 

The Thoracic Duct. 

Structure of the Thoracic Duct 773 

The Right Lymphatic Duct 773 

Applied Anatomy 774 

Lymphatics of the Head, Face, and Neck. 

The Lymphatic Nodes of the Head and Face 774 

Occipital Nodes 774 

Posterior Auricular or Mastoid Nodes.. 774 

Parotid Ljonph Nodes 774 

Internal Maxillary Nodes 776 

Lingual Nodes 776 

Retropharyngeal Nodes 776 

Lymphatic Vessels of the Scalp 776 

Lymphatic Vessels of the Pinna and Exter- 
nal Auditory Meatus 777 

Lymphatic Vessels of the Face 777 

Lymphatic Vessels of the Nasal Fossae 777 

Lymphatic Vessels of the Mouth ■ . . 777 

Lymphatic Vessels of the Tongue 777 

Lymph Nodes of the Neck 777 

Superficial Cervical Nodes 777 

Submaxillary Nodes 778 

Submental or Suprahyoid Nodes 779 

Retropharyngeal Nodes 779 

Deep Cervical Nodes 779 

Lymphatic Vessels of the Skin and Muscles 

of the Neck 780 

Applied Anatomy 780 

The Lymph.atics of the Upper Extremity. 

The Lymph Nodes of the Upper Extremity . 781 

Superficial Lymph Nodes 781 

Deep Lymph Nodes or the Axillary 

Nodes 782 

Lymphatic Vessels of the Upper Extremity 783 

Superficial Lymphatic Vessels 783 

Deep Lymphatic Vessels 784 

Applied Anatomy 784 

The Lymphatics of the Lower Extremity. 

The Lymph Nodes of the Lower Extremity 784 

Anterior Tibial Node 784 

Popliteal Nodes 784 

Inguinal Nodes 785 

Superficial Inguinal Nodes 785 

Deep Inguinal Nodes 786 

Applied Anatomy 786 

The Lymphatic Vessels of the Lower Ex- 
tremity 786 

Superficial Vessels 786 

Deep Vessels 787 



The Lymph.atics of the Pelvis .and 
Abdomen. 

The Parietal Nodes 787 

External Iliac Nodes 787 

Internal IKac or Hypogastric Nodes. . . 787 

Common Iliac Nodes 788 

Lumbar Nodes 788 

Lateral Aortic Nodes 788 

Lymphatic Vessels of the Abdomen and 

Pelvis 789 

Superficial Vessels 789 

Deep Vessels 790 

Lymphatic Vessels of the Perineum and 

External Genitals 790 

The Visceral. Nodes 790 

The Superior Mesenteric Nodes 790 

Mesenteric Nodes 790 

Applied Anatomy 791 

Ileocolic Nodes 791 

Mesocolic Nodes 791 

Inferior Mesenteric Nodes 791 

Lymphatic Vessels of the Abdomen and 

Pelvic Viscera 792 

Lymphatic Vessels of the Stomach 792 

Applied Anatomy 793 

Lymphatic Vessels of the Duodenum . . . 793 
Lymphatic Vessels of the Small In- 
testine 793 

Lymphatic Vessels of the Large Intes- 
tine 794 

Lymphatic Vessels of the Anus and 

Rectum 794 

Lymphatic Vessels of the Liver 794 

Lymphatic Vessels of the Gall-bladder. 795 

Lymphatic Vessels of the Pancreas .... 796 

Lymphatic Vessels of the Spleen 796 

Lymphatic Vessels of the , Suprarenal 

Glands 796 

Lymphatic Vessels of the Urinary 

Organs 796 

Lymphatic Vessels of the Kidney. 796 

Lymphatic Vessels of the Ureter. . 796 

Ljonphatic Vessels of the Bladder. 796 

Lymphatic Vessels of the Prostate 796 

Ljonphatic Vessels of the Urethra. 796 
Lymphatic Vessels of the Reproductive 

Organs 796 

Lymphatic Vessels of the Testes . . 796 
Lymphatic Vessels of the Vas 

Deferens 797 

Lymphatic Vessels of the Ovarj' . . 797 
Lymphatic Vessels of the Fallopian 

Tube 797 

Lymphatic Vessels of the Uterus . . 797 

Lymphatic Vessels of the Vagina. . 797 

The Lymphatics of the Thorax. 

The Parietal Lymph Nodes 798 

Internal Mammary Nodes 798 

Intercostal Nodes 798 

Diaphragmatic Nodes 798 



CONTENTS 



Superficial Lymphatic Vessels of the Tho- 

racic Wall ■• 'J* 

Lymphatic Vessels of the Mammary 

'Gland .■•^;n ■ ■• Vtm 

Deep Lymphatics of the Thoracic Wall. ... 799 

Lymphatic Vessels of the Diaphragm . . 799 

Applied Anatomy '^ 

The Visceral Lymph Nodes «UU 

Anterior Mediastinal Nodes »uu 

Posterior Mediastinal Nodes »uu 



The Visceral Lymph Nodes— 

Tracheobronchial Nodes hUU 

Applied Anatomy ■ • • °0- 

Lymphatic Vessels of the Thoracic Viscera . 802 

Lymphatic Vessels of the Heart 802 

Lymphatic Vessels of the Lungs 802 

Lymphatic Vessels of the Pleura 802 

Lymphatic Vessels of the Thymus 

Gland ■^■■■- 802 

Lymphatic Vessels of the (Esophagus. 802 



THE NERVE SYSTEM. 



The Spinal Cord and Brain, with their 
Meninges. 

Fundamental Facts Regarding the Develop- | 

ment of the Nerve System 804 

Development of Nerve Tissue »OD 

Structure of the Nerve System |U ' 

The Neurone ^ °Xn 

The Dendrites =Yn 

The Axone o^V 

The Collaterals ^^^ 

Nerve Cell Nidi or Nuclei 812 

"Nerve Fibres" and Nerves. 

Origin and Termination of Nerves. ■••■■■■• 81* 
The Supporting Tissue Elements of the 

. Nerve System »{° 

The NeurogUa °J° 

Chemical Composition of Nerves oia 

The Central Nerve System. 

Preliminary Considerations 819 

The Spinal Cord. 

External Morphology of the Spinal Cord. . . 822 

The Enlargements of the Spinal Cord . . . »jA 

Fissures and Grooves of the Spinal Cord ... 82o 

Columns of the Spinal Cord . 82b 

Development of the Spinal Cord. 82^ 

Internal Structure of the Spinal Cord 8-9 

Gray Substance of the Cord 829 

White Substance of the Cord 8dd 

Tracts of the Spinal Cord .•■■•■• gg* 

Ground Bundle of the Dorsal Column . 837 

Ground Bundle of the Lateral Column 839 

Ground Bundle of the Ventral Column 840 

Myelinization of the Axones of the Cord 840 

Applied Anatomy of the Spinal Cord 842 

The Membranes of the Cord. 

The Spinal Dura |43 

The Arachnoid °** 

The Pia of the Cord ■ ■ ■ ■ o4& 

Applied Anatomy of the Membranes oi the 
Cord 



S46 



847 



The Brain or Encephalon. 
General Appearance and Topography of the 

Brain 

Dimensions of the Bram 849 

Weight of the Brain .• • ■ ■ j' V tt ' ' 'i 

The Development of the Bram and the Usual 

Classifioations of its Subdivisions 850 

Brief Consideration of the Phases of Devel- 
opment of the Brain Tube 852 

Forebrain °52 

Midbrain °°^ 

Hindbrain °°g 

Flexures of the Brain Tube :••;.■•, °°^ 

Dorsal and Ventral Laminai or Longitudinal 
Zones of the Brain ood 

Descriptive Anatomy of the Adult Human Brain. 
Parts Derived from the Hindbrain (Rhom- 
bencephalon) 861 

The Medulla Oblongata 8bl 



Parts Derived from the Hindbrain— 

The Pons.. =64 

Fourth Ventricle of the Brain 8o4 

Internal Structure of the Medulla 

Oblongata 867 

Internal Structure of the Pons and Pars 

Dorsalis Pontis /,' ' ■■ i 

Central Connections of the Cranial 

Nerves to the Hindbrain 8/ / 

The Cerebellum ; >; ' ' V „ ■ ' ' ' §So 

Internal Structure of Cerebellum. . 888 

The Cerebellar Peduncles 889 

Weight of the Cerebellum 893 

The Midbrain 893 

External Morphology 894 

Corpora Quadrigemina 894 

Superior Brachium 895 

Internal Geniculate Body 895 

Crura Cerebri 895 

Taenia Pontis 895 

Tractus Peduncularis Transversus 895 

Internal Structure of Midbrain 896 

The Aqueduct and Central Aque- 
duct Gray 897 

Substantia Nigra or Intercalatum . 897 

Corpora Quadrigemina 897 

Tegmentum 897 

Red Nucleus or Rubrum 898 

Fountain Decussation 900 

Crusta or Pes ■ • 900 

Summary of the Gray Masses m the 

Midbrain ;■.■.• ^ 

Deep Origin of Cranial Nerves Arising 

in the Midbrain 900 

Parts Derived from the Forebrain 902 

External Morphology 9U2 

TheThalami 902 

The Pineal Body 9Ub 

Third Ventricle ■■■■_■ 90/ 

External Morphology of the Optic 

Portion of the Hypothalamus . . 908 

Tuber Cinereum 90S 

Pituitary Body or Hypophysis 909 

Lamina Terminahs or Terma 909 

Optic Tract and its Central Con- 
nections 909 

Optic Chiasm 910 

The Cerebral Hemispheres 91- 

External Morphology ■ ■ . ■.■ ■'!'' 

Configuration of Each Cerebral Hemi- 

Cerebral Fissures and Gyres 915 

Cerebral Lobes and Fissures 91b 

The Interlobar Fissures 916 

Frontal Lobe 919 

Parietal Lobe 922 

Occipital Lobe 924 

Temporal Lobe 924 

The Island of Reil 925 

The Rhinencephalon or Olfactory 

Lobe ■■■; ^^^ 

Internal Configuration of the Cerebral 

Hemispheres 931 

The Cortex 932 

The Corpus Callosum 933 

The Lateral Ventricles 93b 

The Choroid Fissure or Rima 940 

The Choroid Plexus of the Lateral 

Ventricles and Velum Interposi- 

turn 940 



CONTENTS 



The Cerebral Hemispheres — Internal Con- 
figuration of — ■ 

The Hippocampus and Fornix .... 942 

The Septum Lucidum 945 

The Anterior Commissure 946 

Gray Masses in the Cerebral Hemi- 
sphere 946 

Intimate Structure of the Cerebral 
Cortex and its Special Types in Dif- 
ferent Regions 951 

Summary of the Cerebral Fibre System 954 

The Olfactory Pathways 958 

Cortical Localization of Function. 

Motor Area , 959 

Sensory Area 960 

Language Area 960 

Association Areas 961 

Craniocerebral Typography 962 

The Meninges or Meningeal Membranes of the 
Brain. 

The Dura of the Brain 964 

Processes of the Dura 966 

The Arachnoid of the Brain 968 

Subarachnoid Space 969 

The Arachnoid Villi or Pacchionian Bodies 970 

The Pia of the Brain 971 

Velum Interpositum or the Tela Chor- 

oidea Superior 971 



The Cranial Nerves. 

The First or Olfactory Nerves. 

Applied Anatomy , 974 

The Second or Optic Nerve. 

■Optic Chiasm 974 

Applied Anatomy 975 

The Third or Oculomotor Nerve. 

Applied Anatomy 977 

The Fourth or Trochlear Nerve. 

Applied Anatomy 978 

The Fifth, Trigeminal, or Trifacial Nerve. 

Gasserian or Semilunar Ganglion 978 

Ophthalmic Nerve 979 

The Superior Maxillary Nerve 982 

The Inferior Maxillary or Mandibular Nerve 987 

Surface Marking 990 

Apphed Anatomy 991 

The Sixth or Abducent Nerve. 

Applied Anatomy 994 

The Seventh or Facial Nerve. 

Applied Anatomy 999 

The Eighth or Acoustic Nerve. 

The Cochlear Nerve 1000 

The Vestibular Nerve 1000 

Applied Anatomy 1001 

The Ninth or Glossopharyngeal Nerve. 

The Superior or Jugular Ganglion 1002 

The Inferior or Petrous Ganglion 1002 

The Gustatory Path 1003 

Applied Anatomy 1003 



The Tenth, Vagus, or Pneumogastric Nerve. 

The Ganglion of the Root or the Jugular 
Ganglion 1005 

The Ganglion of the Trunk or the Inferior 
Ganglion 1005 

Applied Anatomy 1008 

The Eleventh or Spinal Accessory Nerve. 

The Bulbar or Vagal Accessory Part 1009 

The Spinal Portion 1009 

Applied Anatomy 1009 

The Twelfth or Hypoglossal Nerve. 
Applied Anatomy 1012 



The Spinal Neeve.s. 

The Anterior or Ventral Root 

The Posterior or Dorsal Root 

Spinal Ganglia 

Points of Emergence of Spinal Nerves. 
Divisions of Spinal Nerves 



1013 
1013 
1013 
1014 
1014 



The Cervical Plexus. 

The Superficial Branches of the Cervical 

The Deep Branches of the Cervical Plexus, 

Internal Series 

Applied Anatomy 

The Deep Branches of the Cervical Plexus, 

External Series 

Applied Anatomy 



The Brachial Plexus. 

Applied Anatomy 

The Anterior or Ventral Divisions of Thor- 
acic Nerves 

Applied Anatomy 

The Lumbosacral Plexus. 

The Anterior or Ventral Di-visions of the 
Lumbar Nerves 

The Lumbar Plexus 

The Anterior or Ventral Divisions of the 
Sacral and Coccygeal Nerves 

The Sacral Plexus. 
Relations 

The Pudendal Plexus. 

Applied Anatomy 



1023 
1025 



1025 
1026 



1040 
1043 



1044 
1044 

1051 
1053 

1062 



The Sympathetic Nerve System. 

Structure of the Sympathetic System 1063 

The Gangliated Cord. 

Cervicocephalic Portion of the Gangliated 

Cord 1066 

The Superior Cervical Ganglion 1066 

The Middle Cervical Ganglion 1069 

The Inferior Cer^dcal Ganglion 1069 

Applied Anatomy 1069 

Thoracic Portion of the Gangliated Cord 1070 

Lumbar Portion of the Gangliated Cord . . . 1071 

Pelvic Portion of the Gangliated Cord ..... 1072 

The Great Plexuses of the Sympathetic System. 

The Cardiac Plexus 1072 

The CceUac or Solar Plexus 10/3 

The Hypogastric Plexus 1077 

The Pelvic Plexuses 1077 



CONTENTS 



THE OEGANS OF SPECIAL SENSE. 



The Nose. 

The Outer Nose. 
Structure 1079 

The Nasal Fossae. 

The Anterior Nares 1081 

The Posterior Nares 1081 

The Outer Wall 1082 

The Inner Wall lOhS 

The Mucous Membrane 1083 

AppUed Anatomy of the Nose 1085 

The Eye. 

The Capsule of Tenon 1086 

The Tunics of the Bye. 

The Solera and Cornea 1089 

The Sclera 1090 

The Cornea 1090 

The Choroid, Ciliary Body, and Iris 1092 

The Choroid 109.3 

The Ciliary Body 1094 

The Iris 1096 

Membrana Pupillaris 1100 

The Retina or Tunica Interna 1 100 

The Refracting Media. 

The Aqueous Humor 1105 

The Vitreous Body 1105 

The Crystalline Lens 1106 

Applied Anatomy of the Eye 1109 

The Appendages of the Eye. 

The Eyebrows 1112 

The EveHds 1112 

The Eyelashes 1113 

The Meibomian or Tarsal Glands 1114 

The Conjunctiva 1114 

The Lacrimal Apparatus 1115 

The Lacrimal Gland 1115 

The Lacrimal Canals 1116 

The Lacrimal Sac 1116 



The Lacrimal Apparatus — 

The Nasal Duct 1117' 

Surface Form HIT" 

Applied Anatomy 1118 

The Ear. 

The External Ear. 

The Pinna or Auricula 1119 

The Auditory Canal or Meatus 1122 

Applied Anatomy 1124 

The Middle Ear, Drum or Tympanum. 

The Tympanic Cavity 1125' 

The Membrana Tympani 1128 

The Ossicles of the Tympanum 1131 

The Malleus 1131 

The Incus 1132 

The Stapes 1133 

Applied Anatomy •■ 1135 

The Internal Ear or Labyrinth. 

The Osseous Labsointh 1136 

The Vestibule 1136 

The Bony Semicircular Canals 1137 

The Modiolus 1138 

The Membranous LabjTinth 1140 

The Utricle 1140 

The Saccule 1141 

The Membranous Semicircular Canals. 1142 

Structure 1142 

The OHGAN.S of T.aste 1148 

The Skin. 

The Cuticle, Scarf Skin, or Epidermis 1151 

I The Corium, Cutis Vera, Derma, or True 

Skin llo3 

I The Appendages of the Skin. 

The Nails.. 1156 

The Hairs llg?- 

I The Sebaceous Glands 1161 

The Sudoriferous or Sweat Glands 1161 



THE OEGANS OF VOICE AND EESPIRATION. 



The Larynx. 

The Cartilages of the Larynx 1163 

The Ligaments of the Larynx 1167 

Interior of the Larj'nx 1169 

Muscles of the Larynx 1172 

The Trachea .and Bronchi. 

The Risht Bronchus 1176 

The Left Bronchus 1177 

Surface Form }}on 

Applied Anatomy 1180 

The PLETjHa:. 

The Mediastinum or Interpleural Space. 

The Superior Mediastinum 1186 



The Anterior Mediastinum 1186 

The Middle Mediastinum 1186 

The Posterior Mediastinum 1187 

Applied Anatomy 1188 

The Lungs. 

The Apex of the Lung 1188 

The Base of the Lung 11|8 

Surfaces of the Lung 1189 

Borders of the Lung 1190 

Fissures and Lobes of the Lung 1190 

: The Root of the Lung 1193 

Di«sions of the Bronchi 1194 

Surface Form ll™ 

Applied Anatomy 1197 



THE ORGANS OF DIGESTION. 

The Mouth, Oral or Buccal Cavity. ' I The CaHty of the Mouth Proper 

Floor of the Mouth 

The Lips 1200 The Palate 

The Vestibule of the Mouth 1200 The Teeth ^ • ,- ■ , ■ ,u ■ ,, • 

The Mucous Membrane 1200 Temporary. Deciduous, or Milk Teeth, 

The rVippks ; . . 1200 Permanent 1 eeth . .^. ..... . 

The Buccal Glands'. ■.■.■.■.;::: 1200 . Chemical Compo^tion o the Teeth . . . 

The Gums 1200 i Development of the Teeth 



1201 
1201 
1202 
1204 
1205 
1206 
1210 
1212 



CONTENTS 



XXI 



The Tongue. 

The Body of the Tongue 1217 

The Base or Root of the Tongue 1217 

The Apex or Tip of the Tongue 1217 

The Dorsum of the Tongue 1217 

The Margin of the Tongue 1217 

The Under or Inferior Surface of the Tongue 1217 

Development of the Tongue 1221 

Applied Anatomy 1222 

The Salivary Glands. 

The Parotid Gland 1223 

The Submaxillary Gland 1225 

The Sublingual Gland 1226 

Development of the Salivary Glands 1227 

Surface Form 1227 

Applied Anatomy 1229 

The Pharynx. 

The Nasal Part or Nasopharynx 1229 

The Oral Part 1230 

The Tonsils 1230 

Development 1232 

Applied Anatomy 1233 

The Laryngeal Part 1233 

Development of the Pharynx 1234 

Applied Anatomy of the Pharynx 1235 

The (Esophagus. 

Applied Anatomy 1239 

The Abdomen. 

Boundaries of the Abdomen 1241 

Regions of the Abdomen 1242 

The Peritoneum. 
Development of the Peritoneum and 

Alimentary Tract 1245 

Retroperitoneal Fossas 1265 

Applied Anatomy 1268 

The Stomach. 

Openings of the Stomach 1271 

Curvatures of the Stomach 1271 

Surfaces of the Stomach 1271 

■Component Parts of the Stomach 1272 



Interior of the Stomach 1273 

Movement and Innervation of the Stomach . 127!) 

Surface Form 1280 

Applied Anatomy ' 12)50 

The Small Intestine. 

The Duodenum 1282 

Interior of the Duodenum 1286 

Applied Anatomy 1287 

The Jejunum and Ileum 1287 

Meckel's Diverticulum 1288 

Structure of the Villi 1291 

Applied Anatomy of the Small Intestine. . . 1295 

The Large Intestine. 

The Cecum 1296 

The Vermiform Appendix 1298 

The Ileocecal Valve 1301 

Applied Anatomy 1,302 

The Colon 1,303 

Apphed Anatomy 1.306 

The Rectum 1306 

The Anal Canal 1.309 

The Anal Orifice or Anus 1309 

Movements and Innervations of the Intes- 
tines 1312 

Surface Form of the Intestines 1313 

Applied Anatomy of the Intestines 1314 

The Liver. 

Surfaces of the Liver 1320 

Fissures of the Liver 1322 

Lobes of the Liver 1323 

Ligaments of the Liver 1324 

Support and Movability of the Liver 1325 

Abnormalities of the Liver 1326 

The Excretory Apparatus of the Liver 1331 

The Hepatic Duct 1332 

The Gall-bladder 1332 

The Cystic Duct 1333 

The Common Bile Duct 1333 

Surface Relations of the Liver 1334 

Applied Anatomy of the Liver 1335 

The Pancreas. 

Pancreatic Juice 1341 

Surface Form of the Pancreas 1341 

Applied Anatomy of the Pancreas 1341 



THE UEINOGENITAL ORGANS. 



The Urinary Organs. 
The Kidneys. 

Relations of the Kidneys 1343 

Anterior Surface of Right Kidney 1343 

Anterior Surface of Left Kidney 1343 

Posterior Surface of the Kidney 1345 

Borders of the Kidney 1347 

Extremities of the Kidney 1348 

Fixation of the Kidney 1348 

Minute Anatomy of the Kidney 1350 

Variations and Abnormalities of the Kidney 1354 

Surface Form of the Kidney ". 1354 

Applied Anatomy of the Kidney 1355 

The Ureters. 

Applied Anatomy of the Ureters 1358 

The Urinary Bladder. 

Surfaces of the Bladder 1359 

The Fundus or Base 1361 

The Summit or Apex 1361 

The Urachus or Middle Umbilical Ligament 1361 

The Ligaments of the Bladder 1361 

The Interior of the Bladder 1364 

Surface Form of the Bladder 1365 

Applied Anatomy of the Bladder 1366 

The Male Urethra. 

The Prostatic Portion 1366 

The Membranous Portion 1367 



The Penile or Spongy Portion 1368 

Apphed Anatomy 1369 

The Female Urethra 1370 

The Male Reproductive Organs. 

The Testicles. 

The Scrotum 1372 

The Intercolumnar or External Spermatic 

Fascia _ 1374 

The Cremasteric Fascia 1374 

The Infundibuliform Fascia 1374 

The Tunica Vaginalis 1374 

The Inguinal or Spermatic Canal 1375 

The Spermatic Cord 1375 

The Testes 1377 

The Epididymis 1378 

The Tunics of the Testicle 1379 

The Semen 1381 

Applied Anatomy of the Testicle 1382 

The Vas Deferens. 

Organ of Giraldfe 1384 

The Seminal Vesicles. 

Applied Anatomy of the Seminal Vesicles. . 1385 

The Ejttculatory Duels 13S6 



xxu 



CONTENTS 



The Penis. 

The Root of the Penis 1388 

The Body of the Penis 1388 

AppUed Anatomy of the Penis 1390 

The Prostate Gland. 

Applied Anatomy of the Prostate Gland . . . 1395 

Cowper's Glands 1397 

The Female Repboductive Organs. 

The Ovaries. 

The Ovary at Different Ages 1399 

Applied Anatomy of the Ovaries 1401 

The Fallopian Tube or Oviduct. 

Applied Anatomy of the Fallopian Tube . . . 1402 

The Uterus or Womb. q'he Mammary Gland. 

The Fundus of the Uterus 1404 The Nipple 1428 

The Body of the Uterus 1404 Variations in Mammte 1429 

The Neck or Cervix Uteri 1405 Applied Anatomy 1432 

Folds and Ligaments of the Uterus 1406 The Male Breast 1433 

The Uterus at Different Ages 1408 Applied Anatomy 1433 



Abnormalities of the Uterus 1408- 

Changes at a Menstrual Period 1408 

Changes Induced by Pregnancy 1409 

AppUed Anatomy of the Uterus 1411 

The Vagina. 

Relations of the Vagina 1414 

The External Organs. 

The Mods Veneris 1415 

The Labia Majora 1415 

The Labia Minora or Nymphse 1416 

The Vestibule of the Vagina 1416 

The Clitoris 1418 

The Vaginal Bulb 1420 

The Glands of Bartholin 1420 

Development of the Urinary and Generative 

1420 



THE DUCTLESS GLANDS. 



The Thyhoid Gland oh Body. 

Accessory Thyroids 1436 

Apphed Anatomy 1438 

The Parathyroid Gland. 

Embryology. . . . r?T"^-r.._^.^j^^ 1440 

Applied Anatomy ^TT^ : rr^-r^^ 1440 

The Thymus Gland. 

Applied Anatomy 1442 

The Spleen. 
Relations of the Spleen 1444 



Surface Form of the Spleen 1446 

Applied Anatomy 1447 

The Suprabenal Gland ob Adbenal Capsule. 

Accessory Suprarenal Glands 1448 

The Carotid Glands or Carotid Bodies. 

Applied Anatomy 1450 

The Coccygeal Gland ob Body, or Luschka's 
Gland. 

Structure of the Coccygeal Gland 1450 

The Parasympathetic Bodies. . . 1450 



DESCRIPTIVE AND APPLIED ANATOMY. 



INTRODUCTION. 



ANATOMY (dva, apart, and re/iwco, I cut) is the name given to that division 
of natural science which deals with the structure or organization of living 
things. Human anatomy is that division of general anatomy which applies to the 
structure of man, bearing in mind the fact that man is distinguished as a sepa- 
rate genus among primate mammals, an order of vertebrates. 

Man, as a vertebrate, possesses an internal skeleton with a median longitudinal 
axis, which is divided transversely into segments called vertebrse. This vertebral 
axis (spinal column) in the habitually erect position of the human body is sup- 
ported by the pelvic limbs, and is surmounted by the skull. The pelvic limbs 
serve the purposes of progression, while the pectoral limbs are adapted as organs 
of prehension; a distinction common to nearly all primates is the possession of 
an opposable first digit or thumb. The possession of milk glands, rudimentary 
in the male, but well developed and important in the female, relegates the human 
species to the class of mammals. 

The present work is an account of the various parts and organs of the human 
body, being descriptive of their characteristics as revealed by dissection, and, 
with a view toward practical application, certain parts or regions of the body 
are examined in their entirety. These two methods of studying anatomy are 
conventionally termed descriptive anatomy and applied or topographic anatomy. 
Embryology deals with the origin and development of the body and its organs. 
Histology deals with the minute structure of the tissues and organs as revealed 
by the microscope. In the present work only brief accounts of the embryology 
and histology of the organs are interpolated in their proper places; the minute 
details must be sought for in special works upon these subjects. 

The systematic consideration of the parts of the human body requires a foreword 
as to the descriptive terms, nomenclature, and classification employed in anatomy. 

The descriptive terms are names indicative of position and direction. Despite 
the structural homologies discernible among vertebrates in general, there are 
wide differences regarding the natural attitude or position habitually assumed, so 
that whatever is situated " in front" in the erect man is " below" in the quadrupedal 
animal. The use of terms like anterior, posterior, superior, inferior, in front of, 
beneath, has given rise to great ambiguity and confusion whenever applied at one 
and the same time to homologous parts in man and other vertebrates. 

It is essential that the names used in designating structural parts shall be so 
definite that each of the terms shall have but one signification. The study of 
anatomy has been made unnecessarily difficult by a multiplicity of synonyms and 
compound names, when single words would answer all requirements. Further- 
more, many of the terms even now in general use are not equally applicable to 
lower animals and man, a condition which constitutes a great hindrance to ana- 
tomic progress. Various reforms have been proposed, chief of which has been 
that of a commission of the German Anatomic Society, which, in 1895, formulated 
a list of terms, the Basle Nomina Anatomica (BNA), which is unfortunately 

3 (33) 



34 DESCRIPTIVE AND APPLIED ANATOMY 

replete with serious imperfections and inconsistencies. Thus while one of the 
branches of the radial nerve is called the N. cutaneus brachii posterior, the nominal 
suffix of two other branches of the same nerve is dorsalis. It cannot be said 
that the BNA has as yet completely displaced some of the designations in 
common use to that degree which its enthusiastic advocates would wish. The 
ambiguous, confusing, and vague terms will gradually fall into disuse as time 
shows their inutility and better expressions achieve universal adoption. 

For descriptive purposes the liuman body is supposed to be in the erect position, 
the arms hanging by the sides and the palms of the hands directed forward. 
The body, as a whole, as with most vertebrates, consists of two general divisions, 
axial and appendicular; the former is the body proper (soma), the latter comprises 
the limbs (membra). The middle plane of the body is called the meson, from the 
Greek to ftiffou, the middle; while mesal and mesad (ad being the Latin ecjuiva- 
lent of the English -ward) are adjectival and adverbial inflections. The mesal 
plane is also the dorsoventral plane which passes approximately through the 
sagittal suture of the skull, and hence any plane parallel to it is termed a sagittal 
plane. A vertical plane at right angles to the mesal plane passes, roughly speaking, 
through the central part of the coronal suture or through a line parallel to it; 
such a plane is therefore called a coronal plane or frontal plane. A plane at right 
angles to both the mesal and coronal planes is termed a transverse plane. The 
terms anterior and posterior have been employed to indicate the relation of parts 
to the front or back of the body, and the terms superior and inferior to signify the 
relative levels of different structures; but the growing use of data derived from com- 
parative anatomy and embryology in the elucidation of the human structure makes 
it desirable that terms should be employed which may without ambiguity indicate 
relative position in both man and animals. Thus, ventral and dorsal, cephalic and 
caudal (together with their adverbial derivatives ending in -ad), are preferable and 
are thus sometimes used in this edition. Lateral and laterad are general terms per- 
taining to the sides of the body, while dextral and sinistral are specific terms for 
right and left respectively. The terms central (centrad) and peripheral (periph- 
erad) are in general use, though specially applicable to the bloodvessels and the 
nerve system. The common terms "inner" and "outer," "deep" and "superfi- 
cial," "beneath," "under," and so on, are too frequently ambiguous. The use of 
the words ental and ectal, derived respectively from ivzo:; (inward) and iy.ro; 
(outward), and their inflections entad and ectad often serve to avoid such ambi- 
guity. Wherever a series of organs embraces several similar parts, bearing like 
names, the general terms are combined with distinctive prefixes, as, for instance, 
sitpraspinatus and m/raspinatus. The terms proximal and distal refer to the 
attached and free ends of the limbs and their parts, being preferable to the less 
precise and sometimes confusing designations of upper and lower. The other 
aspects (borders or sides) of each limb are variously designated by the terms 
ulnar, radial, anconal, and thenar; tibial, fibidar, patellar, and popliteal. It is 
often convenient to speak of the flexor and extensor aspects of the limb divisions 
and their bones. The designation of parts in the limbs by anterior and posterior is 
still largely employed, though the demands of consistency and logic will probably 
compel the adoption of substitutes more in accord with the nomenclature of com- 
parative anatomy. The classification which is used in the present work is as follows : 

Osteology, or description of the bones. 

Syndesmology, or description of the joints and ligaments. 

Myology, or description of the muscles and fasciae. 

Angiology, or description of the heart and the bloodvessels and lymph vessels. 

Neiirology, or description of the nerve system and organs of special sense. 

Splanchnology, or description of the viscera, comprising the organs of respira- 
tion and phonation, digestion, reproduction, excretion, and internal secretion. 



OSTEOLOGY. 



GENEEAL ANATOMY OF THE SKELETON. 

THE general framework of the body is built up mainly of a series of bones, 
supplemented, however, in certain regions by pieces of cartilage; the bony 
part of the framework constitutes the skeleton. 

In comparative anatomy the term skeleton has a wider application, as in some 
of the lower animals hard, protective, and supporting structures are more exten- 
sively distributed, being developed in association with the integumentary system. 
In such animals the skeleton may be described as consisting of an internal or 
deep skeleton, the endoskeleton, and an external or superficial, the exoskeleton. 
In the human subject the exoskeleton is extremely rudimentary, its only important 
representatives being the teeth and nails. The term skeleton is, therefore, 
confined to the endoskeleton, and this is divisible into an axial part, which includes 
that of the head and trunk, and an appendicular part, which comprises that of 
the limbs. 

In the skeleton of the adult there are 206 distinct bones, as follows: 

f Vertebral column 26 

Axial J Skull 22 

Skeleton j Hyoid bone 1 



iRil; 



libs and sternum 25 

— 74 
Appendicular f Upper limbs 64 

Skeleton \ Lower limbs 62 

— 126 
Auditory ossicles 6 

Total 206 

The patellae are included in this enumeration, but the smaller sesamoid bones 
are not reckoned. 

Bones are divisible, according to their shape, into four classes — long, short, 
flat, and irrecjular. 

Long Bones. — The long bones are found in the limbs, where they form a 
system of levers, which sustain the weight of the trunk and confer the power of 
locomotion and prehension. A long bone consists of a shaft and two extremities. 
The shaft, or diaphysis, is a hollow cylinder, the central cavity being termed the 
medullary canal; the wall consists of dense, compact tissue of considerable thickness 
in the middle part of the shaft, but becoming thinner toward the extremities; 
the cancellous tissue is scanty. The extremities, or epiphyses, are generally ex- 
panded, for the purposes of articulation and to aiTord broad surfaces for muscle 
attachment. They are usually developed from separate centres of ossification 
termed epiphyses, and consist of cancellous tissue surrounded by a thin layer of 
compact bone. The long bones are not straight, but curved, the curve generally 
taking place in two planes, thus affording greater strength to the bone. The 

(35) 



36 



GENERAL ANATOMY OF THE SKELETON 



bones belonging to this class are the clavicle, humerus, radius, uhia, femur, tibia, 
fibula, metacarpal and metatarsal bones, and the phalanges. 

Short Bones. — Where a part of the skeleton is intended for strength and 
compactness, and its motion is at the same time slight and limited, it is divided 
into a number of small bones united by ligaments, and the separate bones are 

short and compressed, such as the bones of 
the carpus and tarsus. These consist of can- 
cellous tissue covered by a thin crust of com- 
pact substance. The patellae also, together 
with the other sesamoid bones, are by some 
regarded as short bones. 

Flat Bones. — Where the principal re- 
Cjuirement is either extensive protection or 
the provision of broad surfaces for the at- 
tachment of muscles, we find the osseous 
structure expanded into broad, flat plates, 
as is seen in the bones of the skull and the 
scapulae. Flat bones are composed of two 
thin layers of compact tissue enclosing be- 
tween them a variable quantity of cancellous 
tissue. In the cranial bones these layers of 
compact tissue are familiarly known as the 
tables of the skull; the outer table is thick 
and tough; the inner table is thinner, denser, 
and more brittle, and hence is termed the 
vitreous table. The intervening cancellous 
tissue is called the diploe. The flat bones 
are: the occipital, parietal, frontal, nasal, lacri- 
mal, vomer, scapula, os innominatum, sternum, 
ribs, and, according to some, the patella. 

Irregular Bones. — The irregular or mixed 
liones are such as, from their peculiar form, 
cannot be grouped under either of the pre- 
ceding heads. Their structure is similar to 
that of other bones, consisting of a layer of 
compact tissue externally and of spongy, 
cancellous tissue within. The irregular 
bones are: the vertebrae, sacrum, coccyx, 
temporal, sphenoid, ethmoid, malar, maxilla, 
mandible, palate, turbinated, and hyoid. 

Surfaces of Bones. — If the surface of 
any bone is examined, certain eminences 
and depressions are seen, to which descrip- 
tive anatomists have given the following 
names. 

These eminences and depressions are of 
two kinds: articular and nonarticular. Well- 
marked examples of articular eminences are 
found in the heads of the humerus and femur, and of articular depressions in the 
glenoid cavity of the scapula and the acetabulum. Nonarticular eminences are 
designated according to their form. Thus a broad, rough, uneven elevation is 
called a tuberosity; a small, rough prominence, a tubercle; a sharp, slender, pointed 
eminence, a spine; a narrow, rough elevation, running some way along the surface, 
a ridge, line, or crest. 




Fig. 1, — General 



of the human skeleton. 



SURFACES OF BONES 



37 



The nonarticular depressions are also of very variable form, and are descril)eil 
as fossae, grooves, furrows, fissures, notches, sulci, etc. These nonarticular emi- 
nences and depressions serve to increase the extent of surface for the attachment 
of ligaments and muscles, and are usually well marked in proportion to the 
muscularity of the subject; the grooves, fissures, and notches often transmit 
vessels and nerves. 




FtG. 2. — Diagram of the structure of compact bone. A small part of a transverse section of the shaft of a long 
bone is shown. At the uppermost part is the periosteum covering the outside of the bone; at the lowermost 
part is the endosteum lining the marrow cavity. Between these is the compact tissue, consisting largely of a 
series of Haversian systems, each being circular in outline and perforated by a central canal. In the first one 
is shown only the area occupied by a system; in the second is seen the concentric arrangement of the lamellae; 
and in the others, respectively, canaliculi; lacuna?; lacunee and canaliculi; the contents of the canal, artery, 
vein, lymphatic and areolar tissue; lamellae, lacunse, and canaliculi; and, finally, all of the structures composing 
a complete system. Between the systems are circumferential and intermediate lamellfe, only a few of which are 
represented as lodging lacunse, though it is to be understood that the lacunie are in all parts. The periosteum 
is seen to be made up of a fibrous layer and a vascular layer, and to have upon its attached surface a stratum of 
cells. From the fibrous layer project inward the rivet-like fibres of Sharpey. (F. H. Gerrish.) 

A prominent process projecting from the surface of a bone which it has never 
been separate from or movable upon is termed an apophysis (from anotlnjae:;, 
an excrescence); but if such process is developed as a separate piece from the 
rest of the bone, to which it is afterward joined, it is termed an epiphysis (from 
i7Tl(}n)acz, an accretion). The main part of the bone, or sliaft, which is formed 
from the primary centre of ossification, is termed the diaphysis, and is separated, 
during growth, from the epiphysis by a layer of cartilage, at which growth in 
length of the bone takes place. Some bones are hollow and contain sinuses, 



38 



GENERAL ANATOMY OF THE SKELETON 



which are spaces for air. Canals, or foramina, are channels or openings in bone 
through which nerves or vessels pass. 

Structure of Bone. — Bone is a highly speciaHzed form cf connective tissue. In reality, it is 
white filjrous tissue, calcified and structurally modified until it becomes osseous tissue. Bone 
is not simply a crude mass resulting from the calcification of cartilage or fibrous tissue; it is a 
distinct tissue, of a definite structure, the constituent parts of which are arranged symmetrically. 
There are two varieties of bone: dense or compact bone {substantia compacta), and can- 
cellous, loose, or spongy bone (substantia spongiosa). 

Compact bone is dense, and is always found upon the exterior of the bony tissue. Even this 
apparently compact tissue is porous; it differs from cancellous bone in its greater densitv and in 
the arrangement of its osseous substance into lamellae. It 
forms practically the entire shafts of the long bones and 
constitutes the outer portion of their extremities and of the 
short, flat, and irregular bones. With the exception of 
enamel and dentin it represents the hardest substance of the 
body, is tough and elastic, and much force is required to 
break it. Compact bone consists of an outer membrane, 
the periosteum, internal to which is seen the osseous 
tissue. 

The periosteum (Fig. 2) is a fibrous membrane adhering 
to the surface of the bone in nearly every part except at the 
cartilage-covered extremities. When strong tendons or 
ligaments are attached to the bone, the periosteum is incor- 
porated with them. By means of the periosteum many 
vessels reach and enter the hard bone through Volkmann's 
canals. This is shown by stripping the periosteum from 
the surface of living bone, when small bleeding points are 
seen, each of which marks the entrance of a vessel from 

Yia. 3. Fibres of Sharpey from the the periosteum. It thus becomes obvious that the loosen- 

p.irietal bone (adult man) isolated by Jng of the periosteum, bv depriving a portion of the bone 
dissociation. (After KoUiker.) r. -. ■ , ^ _. ' j „ ■ t^i, ._ ._u 

01 Its nourishment, may produce necrosis, ine membrane 

is firmly attached to the bone by trabeculfe of fibrous tissue, 
Sharpey's fibres (Fig. 3), which penetrate the bone at right angles to its surface, and carry 
bloodvessels. They do not directly enter the Haversian systems, but only the circumferential 
and intermediate lamellje — parts that are formed by periosteal action. Prolongations from some 
of these vessels reach the Haversian canals, and even the bone marrow. In the extremities of 





Fig. 4. — Transverse section of compact tissue of bone. Magnified about 150 diameters. (Sharpey.) 



a long bone, vessels from the periosteum penetrate the layer of compact bone and reach the 
cancellous tissue. In the newborn and in the young the periosteum is composed of three 
layers: an outer or fibrous layer, containing some bloodvessels, and composed of bundles of 
white fibrous tissue; a middle or flbroelastic layer, containing some bloodvessels, fibrous 
tissue, and much elastic tissue; and an inner or osteogenetic layer, which is very vascular and 
contains numerous cells, which are converted into osteoblasts or bone-forming cells. 



TRANSVERSE SECTION OF COMPACT BONE 39 

Transverse Section of Compact Bone (Fio;. 4). — The osseous tissue consists of cells, 
osteoblasts, and intercellular substance anun^iod in lamellae. In the osseous tissue are 
found Haversian systems, lacunae, canaliculi, and osteoblasts. In the middle of long bones 
is a space, the medullary or marrow cavity, containing the marrow. 

There are four varieties of lamella?: (1) The periosteal, peripheral, circumferential, or 
external; (2) the Haversian, or concentric; (3) the interstitial, ground, or intermediate; 
and (4) the perimeduUary, or internal. The ]5eriosteal lamellfe are sometimes called primary, 
as they are the first to appear, and are formed by the direct transformation of the inner layer 
of the periosteum into bone. In the shaft of a long bone there are several layers of periosteal 
lamellfe, but no one layer is extensive enough to surround the bone completely. Lacunje and 
canaliculi are present. _ _ 

In the outer surface of the layer of periosteal lamellaj depressions exist that are known as 
Howship's foveolae, or lacunae. These depressions a,re made by large cells, called osteoclasts, 
which destroy bone. There are no Haversian canals in this outer layer, but there are some 
larce channels, Volkmann's canals, that convey bloodvessels into the bone and run at right 
angles to the periosteal surface. Many small arteries from the periosteum enter the periphery 
bodi of the shaft and of the epiphyses. 

The Haversian or concentric lamellae 
are circular layers arranged around a 
central space, or canal, known as the 
Haversian canal. There is no fixed 
number of these layers, there being 
usually from five to ten. The layers of 
each system are parallel to one another. 





Fig. 5. — Nucleated bone cells (osteoblasts) and 
their processes, contained in the bone lacuna and 
their canaliculi respectively. From a section 
through the vertebra of an adult mouse. (Klein 
and Noble Smith.) 



Fig. 6. — Combined transverse and longitudinal section of 
compact bone. CH. Longitudinal Haversian canal and 
anastomosing canals, o. Communicating with medullary 
cavity. Si. Intermediate systems. Spe. Circumferential 
lamella?. Spi. PerimeduUary lamelte. os. Osteoblasts. 
(Poirier and Charpy.) 



but the layers of different systems cross at va rious angles. Between these layers are small, irreg- 
ular spaces called lacunae; and extending radially nut from the lacunte and piercing the various 
lamellas are delicate canals known as canaliculi, which connect the lacuna?. The lacuna nearest 
to the Haversian canal communicates with it by means of canaliculi; and canaliculi also com- 
municate with other Haversian systems. The Haversian canal contains bloodvessels— an artery 
or a vein, or both — and a nerve. The vessel in the canal is covered with endothelial cells, and the 
canal itself is lined with them. The space thus formed is a lymph channel, and into these chan- 
nels the canahculi empty. Beneath the periosteum and at the periphery of the medullary cavity 
there are lymph spaces that are in direct communication with the canaliculi of the Haversian 
systems. In each lacuna is a bone cell — a corpuscle that almost fills the space, and sends arms, 
or processes, out into the canaliculi (Fig. .5). This bone cell is an osteoblast. 

The interstitial or intermediate lamellae occupy the spaces between the Haversian systems. 
They represent the remains cf p. riiihcral lamell*. ' They are usually short and very irregular, 
but possess lacunae and canaliculi, which are arranged as in the Haversian systems. 

The perimeduUary lamellae are irregular and few in number. They surround the marrow 
cavity, and in areas mav be interrupted. Lacunse, canaliculi, and osteoblasts are present. 

Lining the marrow cavity surface of the bone is a membrane, the endosteum, that resembles 
the periosteum in structure, but is not cjuite so prominent. 

The osteoblasts are irregular, flattened, stellate masses of protoplasm, possessing a number 
of processes. The protoplasm is granular, and each cell contains a large and distinct nucleus. 



40 



GENERAL ANATOMY OF THE SKELETON 



Osteoblasts are met with in the deeper layer of the periosteum, in the endosteum, and in the 
lacunae. 

Longitudinal Section of Compact Bone (Figs. 6 and 8). — We do not see concentric rings, 
as in a transverse section, but rows of lacuna; parallel to the course of the Haversian canals — and 
these canals appear like half tubes instead of circular spaces. The tubes are seen to branch 
and communicate, so that each separate Haversian canal runs only a short distance. In other 
respects the structure closely resembles that of a transverse section. 

Cancellous bone is found in the interior of flat and irregular bones and forming the bulk 
of the extremities of the long bones. It consists of anastomosing spicules of bone forming a 
meshwork for the red marrow. The spicules have a fibrillar structure, and contain lacunae and 
canaliculi, but no Haversian systems. 

In the epiphyses the spicules are placed, as a rule, at right angles to the planes of the articular 
surface (the lines of greatest pressure) ; these are bound together by other spicules that correspond 
in direction to the planes of the articulation (the lines of greatest tension). Those spicules 
nearer the marrow cavity are usually heavier and stronger (Fig. 181). 




-Cells of red marrow of the gu 
i-t. Erythroblasts 



Marrow. — There are three varieties: red, yellow, and mucoid. 

Red marrow {medulla ossium rubra) is found in the diploe of the cranial bones, in the cancellous 
tissue of the vertebrse, ribs, and sternum, and in the extremities of the long bones. Red marrow 
contains much less fat and is less solid than yellow marrow. It consists of a delicate net- 
work of retiform connective tissue, supporting a dense capillary plexus; some fat; and numer- 
ous cellular elements. Surrounding the marrow is the endosteum. The cellular elements 
of red marrow (Figs. 7 and 12) comprise four main groups: (1) Marrow cells, or myelocytes, 
which are granular protoplasmic masses, capable of ameboid movements, and containing large 
nuclei. They are not found in normal blood, but are abundant in leukemia. (2) Small 
nucleated, reddish cells called erythroblasts are found; they resemble the nucleated red cells 
of the blood of the embryo; eventually by the loss of their nuclei they become normal red 
blood corpuscles. (3) Nonnucleated red blood corpuscles; and (4) giant cells, containing one 
or more nuclei — the osteoclasts — complete the cellular elements. In addition there are a large 
number of leukocytes, or white blood cells, i. e., polynuclear cells, eosinophiles, and basophiles. 

Yellow marrow is found in the shafts of long bones of adults, and differs from the preceding 
in the presence of a great quantity of fat and a corresponding decrease in the number of cellular 
elements. 

Gelatinous or mucoid marrow is formed by the absorption of the fat and the cellular 
elements of yellow marrow, and by the serous infiltration of the intercellular substance. It is 
produced by starvation, old age, and certain pathological conditions. Neither yellow nor 
mucciid marrow are blood-cell forming in function. 

Bloodvessels of Bone. — Small arteries derived from the periosteum enter Volkmann's canals 
and pass to the Haversian canals and ultimately to the marrow. The cancellous tissue is sup- 
plied by fewer but larger vessels, which are derived from the periosteum, and which often pene- 
trate the covering of the compact bone and ramify in the cavities of the spongy tissue. 

The marrow is supplied by a large artery (sometimes more than one) called the nutrient 
artery. It enters the bone by the nutrient foramen, which is usually near the centre of the 
shaft, runs in an oblique canal through the compact substance, giving off branches to this 



CHEMICAL COMPOSITION OF BONE 



41 



structure, and entering the medullary cavity, sends branches toward the extremities, thus 
forming capillary plexuses in the marrow. These branches communicate with branches from 
the periosteal vessels The walls of the \essels are ^erv thin, the venous blood enters the 
spaces of the led marrow and the current becomes extremely slow. Small \eins collect the 
venous blood and emii^c tiom the bone 










_. _ „iuuii lluiifeitudmal seLtioii thiouth tliL diapln Is ut tliL hu 

with pigment which la here black Ha\ ersian canalb aie cut longitudin \Uj 



\11 ctnals are filled 
90 (tozymonowicz ) 



Veins emerge from the long bones in three places: (1) One or two large veins accompany 
the nutrient artery. (2) Numerous veins emerge at the articular extremities. (3) Many small 
veins arise in and emerge from compact substance. The latter two classes do not accompany 
arteries. The veins in the marrow and in the bone are devoid of valves; but immediately after 
emerging from the bone they have numerous valves. In the flat cranial bones the veins are 
numerous and large. 

The lymphatics are chiefly periosteal; but some have been demonstrated as entering the bone, 
nlong with the vessels, and running in the Haversian canals. 

Nerves, meduUated {myelinic) and nonmeduUated (amyelinic) , are found in bone. They are 
distributed freely to the periosteum, and some of the fibres terminate in this structure as Pacinian 
corpuscles. Nerves accompany the nutrient arteries into the interior of the bone, and also reach 
the marrow from the periosteum by w^ay of Volkmann's canals and the Haversian canals. They 
certainly supply the arterial coats and possibly ramify about the osteoblasts. Nerves are most 
numerous in the articular extremities of the long bones, in the vertebrae, and the large flat bones. 

Chemical Composition of Bone. — Bone consists of about 36 per cent, of animal {organic) 
and about 64 per cent, of earthy {inorganic) substance intimately combined. 

The animal part may be obtained by immersing the bone for a considerable time in dilute 
mineral acid, after which process the bone comes out exactly the same shape as before, but per- 
fectly flexible, so that a long bone (one of the ribs, for example) can easily be tied into a knot, 
if now a transverse section is made, the same general arrangement of the Ha\'ersian canals, 



42 



GENERAL ANATOMY OF THE SKELETON 



lamelliE. lacunte, and canaliculi is seen, though not so plainly as in the ordinary section. The 
animal basis is lararely composed of ossein, or fat collagen. When boiled with water, especially 
under pressure, fat collagen is almost entirely resolved into gelatin. 

The earthy part may be obtained by calcination, in which process the animal matter is com- 
pletely burned out. The bone will still retain its original form, but it will be white and brittle, 
will have lost about one-third of its original weight, and will crumble upon the slightest pressure. 
The earthy matter confers on bone its hardness and rigidity, and the animal matter its tenacity. 
The mineral matter consists chiefly of calcium phosphate, forming about two-thirds of the 
weight of bone. 

Ossification and Growth of Bone. — For the early development of the skeleton the 
reader is referred to text-books on embryology. Embryonic connective-tissue cells of the meso- 

blast develop membrane. Membrane may become 
bone directly or cartilage may be deposited, which 
cartilage by the process of ossification is changed into 
bone. The tissue which is eventually to become bone 
contains cellular elements which evolve into osteo- 
blasts, or bone-forming cells. Osteoblasts exist in the 
connective tissues which become bone by intramem- 
branous ossification, and in the deeper layers of the 
tissue called perichondrium which invests cartilage 
and which becomes the osteogenetic layer of the peri- 
osteum. In view of the fact that in the fetal skeleton 
some bones are preceded by membrane (parietal bones, 
frontal bone, upper part of tabular portion of occipital 
bone, most of the bones of the face), and others are pre- 
ceded by rods of cartilage (the long bones), two kinds 
of ossification are described — viz., the intramembra- 
nous and the intracartilaginous. 

Intramembranous Ossification. — In the case of 
bones which are developed in membrane no cartilagi- 
nous mould precedes the appearance of the bone tissue. 
The membrane, which occupies the place of the future 
bone, consists of white, fibrous connective tissue, and 
ultimately forms the periosteum. At this stage it is seen 
to be composed of fibres and granular cells in a matrix. 
The outer portion is more fibrous, while internally the cells or osteoblasts predominate; the whole 
tissue is quite vascular. At the outset of the process of bone formation a little network of bony 
spicules is first noticed radiating from the point or centre of ossification. When these rays of 




Fig. 9. — Schematic diagram, showing epi- 
physis and diaphysis and line of ossification, 
Ev. Epiphysis of endochondral bone. zpt. 
Zone of proliferation. 7C. Zone of calcifica- 
tion, ca. Cartilage. (Poirier and Charpy.) 



Union q 

adjacent 




Fig. 10, — Part of the grow 



V Bony 

^^^iT^ " spicules. 

ng edge of the developing parietal bone of a fetal cat, (After J. Lawr 



growing bone are examined with a microscope they are found to consist at their growing point 
of a network of fine, clear fibres and granular corpuscles, with an intervening ground substance 
(Pig. 10). The fibres are termed osteogenetic fibres, and are made up of fine fibrils differing 



INTJRAMEMBBANO US OSSIFXCA TION 



43 



little from from those of white fibrous tissue. Like them, they are probably deposited in the matrix 
through the influence of the cells — in this case the osteoblasts. The osteogenetic fibres soon 
assume a dark and granular appearance from the deposition of calcareous granules in the fibres 
and in the intervening matrix, and as they calcify they are found to enclose some of the granular 






C'o^ 




Fig. 11. — Longitudinal section tlirnuch tlie second phalanx of tlie fincer of a seven months' human embryo. 
Stained in hematoxylin and eosin. X 104. A. Periosteum. B. Primary areola. C. Periosteal bone. D. Sec- 
ondary areola and marrow. E, Calcareous material. F^ Endochondral bone. (Szymonowicz.) 

corpuscles, or osteoblasts. By the fusion of the calcareous granules the bony tissue again assumes 
a more transparent appearance, but the fibres are no longer so distinctly seen. The involved 
osteoblasts form the corpu.scles of the future bone, the spaces in which they are enclosed con- 
stituting the lacuniE. As the osteogenetic fibres grow out to the periphery they continue to 
ossify and give rise to fresh bone spicules. Thus, a network of bone is formed, the meshes of 




Fig. 12. — Section through the red bone 
B. Eosinophiles. C. Nucleated red blood 



__ a rabbit. Biondi's stain. X 640. .4. Jlyelocytes. 
puscles. D. Giant cells. E. Myelocyte. (Szymonowicz.) 



which contain the bloodvessels and a delicate connective tissue crowded with osteoblasts. The 
bony trabecule thicken by the addition of fresh layers of bone formed by the osteoblasts on their 
surface, and the meshes are correspondingly encroached upon. Subsequently successive layers 
of bony tissue are deposited under the periosteum and around the larger vascular channels. 



44 



GENERAL ANATOMY OF THE SKELETON 



which become the Haversian canals, so that the bone increases much in thickness. The process 
spreads laterally to the region of the future suture, and here between the various bones a layer 
of fibrous tissue, the cambium layer, is maintained until the full size of the bone is reached. 
The cambium layer then ossifies and the bone ceases to grow at its edges. 

Intracartilaginous Ossification. — .Just before ossification begins the bone is entirely carti- 
laginous, and in the long bone, which may be taken as an example, the process commences in 
the centre and proceeds toward the extremities, which for some time remain cartilaginous. 
Subsequently a similar process commences in one or more places in those extremities and 
gradually ossifies them. The extremities do not, however, become joined to the shaft by bony 
tissue until growth has ceased, but are attached to it by a layer of cartilaginous tissue termed the 
epiphyseal cartilage. 

The first step {proliferation) in the ossification of the cartilage is that the cartilage cells, at the 
point where ossification is commencing and which is termed a centre of ossification, multiply, 
enlarge, and arrange themselves in rows (Fig. 11). The matrix in which they are embedded 



■>^^ 



\-^ 



/ 



Fig. 13. — Cross-section of a developing bone of a human fetus of four montlis, a. Periosteum, h. Boundary 
between endochondral and periosteal bone. c. Perichondral bone. d. Remains of area of e&lcification. 
c. Endochondral bone, f, f. Bloodvessels, g. g'. Developing Haversian spaces. A. Marrow, i. Bloodvessel. 
(Radasch, after Stohr's Histology.) 

increases in quantity, so that the cells become further separated from each other. A deposit 
of calcareous material (calcification) now takes place in this matrix, between the rows of cells, 
so that they become separated from each other by longitudinal coliunns of calcified matrix. 
These columns are connected to one another by transverse bars of calcareous substance, and 
present a granular and opaque appearance. In the calcareous areas the cartilage cells repro- 
duce so rapidly that a number of cells are seen in each large lacuna, or space, which is called a 
primary areola. This process is succeeded by destruction of some of the columns between the 
smaller spaces, forming thus a fewer number of larger spaces, the secondary areolae. Some of 
the cells within the areolse disappear, others become osteoblasts, which appty themselves to the 
columns and secrete a thin veneer of osseous tissue upon the calcareous matter; still others 
of these cells become osteoclasts. 

At the same time that this process is going on in the centre of the solid bar of cartilage of 
which the fetal bone consists, certain changes are taking place on its surface. This is covered 
by a very vascular membrane, the perichondrium, entirely similar to the embryonic connective 
tissue already described as constituting the basis of membrane bone, on the inner or cartilage 



INTRA CA R TIL A GINO US OSSIFICA TION 



45 



siirface of which the cells become osteoblasts, or bone-forming cells. By the agency of these 
cells a thin layer of bony tissue is being formed between the outer membrane, now the periosteum, 
and the cartilage by the intramembraiious mode of ossification just described; this constiiuics 
the first periosteal lamella. These two processes go on simultaneously. The second stan-e 
i vascularization) consists in the prolongation into the cartilage of processes of the deeper or 
osteogenetic layer of the periosteum, these processes consisting of bloodvessels and cells — 
osteoblasts, or bone formers, and osteoclasts, or bone destroyers. The latter are similar to 
the giant cells (myeloplaques) found in marrow, and they excavate passages through the new- 
formed bony layer by absorption, and ]3ass through it into the areolae. Wherever these processes 
come in contact with the calcified walls of the primary areolse they absorb it, and thus cau.se a 
fusion of the original cavities and assist in the formation of larger spaces, which are termed the 
secondary areolae (Sharpey), or medullary spaces. These secondary spaces become filled with 
enibryoni:' marrow, consisting of ostenlilasts, vessels, a few leukocytes, and a few myelocytes. 

Tiie first periosteal lamella is rapiiily followed by the formation of others of the same nature, 
the osteoblasts secreting the lamellre remaining between the successive layers with their pro- 
cesses passing from one to the other. The spaces occupied by these cells are the lacunae and the 
small channels occupied by the processes are the canaliculi. A periosteal lamella is not smooth 
and regular and does not extend completely around the developing bone, but meets others 
that aid in completing the circle. The irregularities are due to projecting processes of bone that 
meet others and enclose small, irregu- 
lar, longitudinal canals, which contain 
vessels and primitive marrow, and 
are the primitive Haversian canals. 
These are also seen at the junctions 
of the lamellae (Fig. 13). The osteo- 
clasts of the primitive marrow apply 
themselves to the walls of the canals 
and absorb the osseous tissue until a 
comparatively large and regular 
canal is formed, and within this canal 
the osteoblasts secrete successive 
concentric layers of bone until a 
small central canal alone remains 
which contains a little marrow and 
the vessels. This canal is the true 
Haversian canal. The concentric 
lamelke are the Haversian lamellae, 
between which the osteoblasts remain 
in their lacunae and radiating can- 
aliculi. The remains of the peri- 
osteal lamellae between the Haversian 
systems constitute the interstitial 
lamellae (Fig. 6). Within the centre 
of the rod of devebping bone the osteoclasts meanwhile destroy the trabeculae of calcific 
material covered by osseous tissue, and thus is formed one common cavity — the beyinning 
of ilie medullar!/ cavity. The marrow then forms one common mass in the centre of the bone, 
and the surrounding fibrous tissue becomes a second periosteum, or endosteum, which sur- 
rounds the marrow and secretes incomplete lamellae, thus bounding the marrow cavity as the 
perimedullary lamellae. All of the above osseous tissue is merely temporary in the growth of 
the bone thickness. As can now be readily seen, the long bones increase evenly in thickness by 
the periosteal method, while increase in length is due entirely to the intracartilaginous method. 

.Such are the changes which may be observed at one particular point, the centre of ossification. 
While they have been going on here a similar process has been set up in the surrounding parts 
and has been gradually proceeding toward the ends of the shaft, so that in the ossifying bone 
all the changes described above may be seen in different parts, from the true bone in the centre 
of the shaft to the hyaline cartilage at the extremities. The bone thus formed differs from the 
bone of the adult in being more spongy and less regularly lamellated. 

As more and more bone is removed by this process of absorption from the interior of the bone 
to form the medullary canal, so more and more bone is deposited on the e.xterior by the peri- 
osteum, until at length the bone has attained the shape and size which it is destined to retain 
during adult hfe. As the ossification of the cartilaginous shaft extends toward the articular 
ends it carries with it, as it were, a layer of cartilage, or the cartilage grows as it ossifies, and thus 
the bone is increased in length. During this period of growth the articular end, or cpiphyxis, 
remains for some time entirelv cartilaginous; then a bony centre appears in it, and it undergoes 
the same process of intracartilaginous ossification; the cancellous bone of the extremities of the 
processes of the bones is never completely removed to form a single marrow cavity, but the 




Fig. 14. — Osteoblasts from the parietal bone of a human eflfcryo 
thirteen weeks old. a. Bony septa with the cells of the lacunae. 
h. Layers of osteoblasts, c. The latter in transition to bone cor- 
puscles. (-\fter Gegenbaur.) 



46 GENERAL ANATOMY OF THE SKELETON 

spaces become somewhat enlarged as the bones grow. The epiphyses remain separated from the 
shaft by a narrow cartilaginous {cambium) layer for a definite time (Fig. 9). This layer ulti- 
mately ossifies, the distinction between shaft and epiphysis is obliterated, and the bone assumes 
its completed form and shape. The same remarks also apply to the processes of bone which are 
separately ossified, such as the trochanters of the femur. The bones, having been formed, con- 
tinue to grow until the body has acquired its full stature. 

The number of ossific centres varies in different bones. In most of the short bones ossification 
commences at a single point in the centre, and proceeds toward the circumference. In the long 
bones there is a central point of ossification for the shaft or diaphysis; and one or more for each 
extremity, the epiphysis. That for the shaft is the first to appear. The union of the epiphyses 
with the shaft takes place in the reverse order to that in which their ossification began, with 
the exception of the fibula, and appears to be regulated by the direction of the nutrient artery 
of the bone. Thus, the nutrient arteries of the bones of the arm and forearm are directed toward 
the elbow, and the epiphyses of the bones forming this joint become united to the shaft before 
those at the shoulder and wrist. In the lower limb, on the other hand, the nutrient arteries 
pass in a direction from the knee; that is, upward in the femur, downward in the tibia and fibula; 
and in them it is observed that the upper epiphysis of the femur and the lower epiphysis of the 
tibia and fibula become first united to the shaft. 

Where there is only one epiphysis, the nutrient arter}' is directed toward that end of the bone 
where there is no additional centre, as toward the acromial end of the clavicle, toward the distal 
end of the metacarpal bone of the thumb and great toe, and toward the proximal end of the other 
metacarpal and metatarsal bones. 

Besides these epiphyses for the articular ends, there are others for projecting parts or processes, 
which are formed separately from the bulk of the bone. For an account of these the reader 
is referred to the description of the individual bones in the sequel. 

A knowledge of the exact periods when the epiphyses become joined to the shaft is often 
of great importance in medicolegal inquiries. It also aids the surgeon in the diagnosis of 
many of the injuries to which the joints are liable; for it not infrequently happens that on the 
application of severe force to a joint the epiphysis becomes separated from the shaft, and such 
an injur}' may be mistaken for a fracture or dislocation. 

Applied Anatomy. — It has been stated above that the bones increase first in length by ossi- 
fication continuing to extend in the epiphyseal cartilage, which goes on growing in advance of 
the ossifying process; and secondly in circumference by deposition of new bone from the deeper 
layer of the periosteum. A thorough realization of these facts is essential to the student, when 
he comes to consider the various pathological changes which affect bone. Anything which inter- 
feres with the growth at the epiphyseal line will lead to a diminution in the length which the bone 
should attain in adult life, and similarly anything which interferes with the growth from the 
deeper layer of the periosteum will result in a disproportion in the thickness of the bone. Thus, 
separation of the epiphyses, septic or tuberculous disease about the epiphyseal line, and excisions 
involving the epiphyseal line, will result in varying amounts of shortening of the bone, as com- 
pared with that of the opposite side; whereas separation or imperfect nutrition of the periosteum 
results in defective growth in circumference. 

It is thus obvious that a careful study of osseous development is of the very greatest utility 
in the proper understanding of bone disease; and, moreover, that an accurate knowledge of 
the blood supply of a long bone has many important bearings. The outer portion of the compact 
tissue being supplied by periosteal vessels, which reach the bone through muscle attachments, 
it follows that where the muscles or muscle attachments are well developed, and therefore amply 
supplied with blood, the periosteum will ako be well nourished and the bones proportionately 
well developed in girth; this is well seen L. strong, muscular men with well-marked ridges on 
the bones. Conversely, if the muscle development be poor, the bones are correspondingly 
thin and light, and if from any cause a limb has been paralyzed from early childhood, all of the 
bones of that extremity are remarkable for their extreme thinness — that is to say, the periosteal 
blood supply has been insufficient to nourish that membrane, and consequently very little new 
osseous tissue has been added to the bones from the outside. 

The best example of this condition is seen in connection with the disease known £(s infantile 
paralysis, where a limb becomes paralyzed at a very early period of childhood, where the muscles 
become flaccid and atonic, and where the blood supph' is in consequence very greatly diminished. 
In such cases, although the limb does continue to grow in length from the epiphyseal lines, its 
length is considerably less than on the normal side, as a result of the imperfect nutrition; but the 
most striking feature about all the long bones of the limb is their remarkable tenuity, little or 
no addition having been made to their diameters. 

In cases where the periosteum has been separated from the compact tissue by extensive 
injury or inflammatory exudation, necrosis or death of the underlying portion of bone takes 
place, due to interference with the blood supply, and the dead portion or sequestrum has to be 
subsequently separated and cast off. 

Cases, however, occur in which the inflammatory process affects the whole oi a great portion 



APPLIED ANATOMY 



47 



of the diaphysis of a long bone, and here extensive necrosis of the affected portion takes place, 
and the condition goes by the name of acute infective periostitis. Where this occurs the shaft of 
the bone dies very rapidly, especially if the singly nutrient artery be thrombosed at the same time. 
The pus which has formed beneath the periosteum is set free by timely excision, or burrows to 
the surface; the periosteum then falls back on the necrosed diaphysis and rapidly forms a layer 
of new periosteal bone, surrounding the sequestrum. This layer is called the involiicrum, 
and the openings in it through which the pus escapes the cloacw. When the inflammatory 
process affects mainly the medullary canal, the condition is spoken of as osteomyelitis, and the 
two conditions very frequently co-exist, and then go by the name of acute infective necrosis of 
hone or acute diaphysitis. When the medullary cavity is filled with pus, septic thrombosis of 
the veins in the Haversian canals takes place, and there is a very great danger of septic emboli 
being separated and carried into the general circulation, thus setting up a fatal pyemia. In 
fact, pyemia is more frequently due to septic bone conditions than to any other cause. 

In the preantiseptic days pyemia frequently resulted from amputations, when the medullary 
canal of a long bone was opened by the saw cut. Osteomyelitis ensued, and if the patient sur- 
vived, a tubular sequestrum of the divided shaft subsequently separated. 

A proper understanding of the epiphyses is of the utmost possible importance to the student, 
and greatly simplifies many of the problems in the pathology of bone disease. 

Speaking generally, the long bones have at either end an epiphysis from the cartilage of which 
growth occurs, and hence the shaft of the bone increases in length at both ends. In every case, 
however, one epiphysis is the more active, and also continues in its activity for a longer time. 
This actively growing epiphysis is always the one from which the nutrient foramen in the diaphy- 
sis is directed, and it unites to the shaft at a later date. It follows, therefore, that the increase 
in length of a long bolie is largely dependent on the epiphysis, and hence anything which inter- 
feres with the growth from this epiphyseal line at any time prior to the union of the epiphysis 
with the shaft must result in a cessation of growth in length of that bone. Thus, when dealing 
with disease in the neighborhood of this actively growing epiphysis very great care should be 
taken not to excise or destroy its line of union with the shaft. These epiphyses are particularly 
prone to become the seat of tuberculous disease, which especially tends to attack the soft, highly 
vascular cancellous tissue. 

Again, the actively growing epiphyseal line is the portion of a long bone which is in the vast 
majority of cases affected by tumor growth in bone, whether it be innocent or malignant, the 
former (viz., osteoma) usually appearing about puberty, and the latter (viz., sarcoma) usually 
toward the end of the active period of epiphyseal growth. 

Epiphyseal growth, moreover, has to be considered by the surgeon when he is about to ampu- 
tate in a child. If tlie amputation is being performed through a bone, the actively growing 
epiphysis of which is at the upper end, and which will continue to grow for many years (i. e., 
humerus and tibia), it will be necessary to make allowance for this and to cut the flaps long; as 
otherwise, owing to continued growth, the sawed end of the bone will ultimately project through 
the stump, and a condition known as "conical stump" will result. This requires removal of a 
further portion of the bone. 

An inflammatory condition termed acute epiphysitis also occurs, although it is not so frequent 
as the acute infective conditions of the diaphysis, owing to the freer blood supply of the epiphysis; 
in late years it has been shown that acute epiphysitis in children is very frequently the result of 
a pneumococcal infection, and it may pass on to complete separation of the epiphysis. In this 
connection it is worthy of note that some of the epiphyseal lines lie entirely within the capsules 
of their corresijonding joints, in other cases entirely without the capsules; and it must follow 
that in the former case epiphyseal disease, acute or chronic, becomes, ipso facto, practically 
synonymous with disease of that joint. The best examples of intracapsular epiphyses are those 
of the head of the femur and the head of the humerus, and the vast majority of all cases of 
tuberculous disease of the hip starts as a tuberculous epiphysitis about the intracapsular 
epiphyseal line of the femur; again, cases of acute septic arthritis of the shoulder- or hip-joint 
generally have their origins in these intracapsular epiphyseal lines, and often result in separa- 
tion of the affected epiphysis. The other class, or extracapsular epiphysitis, when diseased, do 
not tend to involve the neighboring joint so readily; and it should be the surgeon's duty to keep 
the disease from involving the joint. For example, the trochanteric epiphysis of the femur is 
extracapsular as regards the hip-joint, and the epiphyseal line of the head of the tibia is well 
below the level of the knee-joint, and should a chronic tuberculous abscess form in the latter 
situation, it should be attacked from the outside before it has time to spread up and involve the 
cartilage of the head of the tibia. It is, therefore, of great surgical interest to note in every case 
the relations which the various epiphyseal lines bear to their respective joint capsules. 



48 SPECIAL ANATOMY OF THE SKELETON 

SPECIAL ANATOMY OF THE SKELETON. 

THE VERTEBRAL OR SPINAL COLUMN, OR THE SPINE 
(COLUMNA VERTEBRALIS). 

The vertebral column is a flexuous and flexible column formed of a series of 
bones called vertebrae. 

The vertebrse are thirty-three in number, and have received the names cervical, 
thoracic, lumbar, sacral, and coccygeal, according to the position which they occupy; 
seven are found in the cervical region, twelve in the thoracic, five in the lumbar, 
five in the sacral, and foui- in the coccygeaTf" 

This number is sometimes increased by an additional vertebra in one region, or 
the number may be diminished in one region, the deficiency being supplied by 
an additional vertebra in another. These observations do not apply to the cervical 
portion of the vertebral column, as the number of bones forming it is rarely 
increased or diminished. 

The vertebrse in the upper three regions of the spine remain separate through- 
out life, and are known as true or movable vertebra; but those found in the sacral 
and coccygeal regions are firmly united in the adult, so as to form two bones — 
five entering into the formation of the upper bone or sacrum, and four into the 
terminal bone of the spine or cocc3rx. The fused vertebra are known as false 
or immovable vertebrae. 

With the exception of the first and second cervical, the true or movable verte- 
brae present certain common characteristics which are best studied by examining 
one from the middle of the thoracic region. 

GENERAL CHARACTERS OF A VERTEBRA. 

A typic vertebra consists of two essential parts — an anterior solid segment, the 
body, and a posterior segment, the arch (arcus vertebrae), or the neural arch. The 
arch is formed of two pedicles &ad two laminae, supporting seven processes — viz., 
four articular, two transverse, and one spinous. 

The bodies of the vertebrse are placed one upon the other, forming a strong 
pillar for the support of the skull and trunk; the arches forming a hollow 
cylinder behind the bodies for the protection of the spinal cord. The different 
vertebrae are connected by means of the articular processes and the intervertebral 
fibrocartilages; while the transverse and spinous processes serve as levers for the 
attachment of muscles which move the different parts of the vertebral column. 
Lastly, between each pair of vertebrte apertures (foramina intervertehralia) exist 
through which the spinal nerves pass. 

The Body (corpus vertebrae) is the largest part of a vertebra. Its tipper 
and lower surfaces are flattened and rough for the attachment of the intervertebral 
fibrocartilages, and each presents a rim around its circumference. In front it 
is convex from side to side, concave from above downward. Behind it is flat 
from above downward and slightly concave from side to side. Its anterior 
surface is perforated by a few small apertures, for the passage of nutrient vessels; 
while on the posterior surface is a single large, irregular aperture, or occasionally 
more than one, for the exit of veins, the venae basis vertebrae, from the body of 
the vertebra. 

Pedicles (radix arcus vertebrae). — The pedicles are two short, thick pieces 
of bone, which project backward, one on each side, from the upper part of the 



THE CERVICAL VERTEBRA 49 

body of the vertebra, at the line of junction of its posterior and lateral surfaces 
and form the root of the vertebral arch. The concavities above and below 
the pedicles are the superior and inferior intervertebral notches [iucisura vertebralis 
superior et inferior); they are four in number, two on each side, the i nferior on ps 
being generalTj^Jhe-deeper. When the vertebrae are articulated the notches of 
each contiguous pair of bones form the intervertebral foramina (foramina inter- 
vertebralia), which communicate with the vertebral canal and transmit the spinal 
nerves and bloodvessels. 

Laminae. — ^The laminae are two broad plates of bone which complete the 
neural arch by fusing together in the middle line behind. They enclose a foramen, 
the spinal or vertebral foramen {foramen vertehrale), which serves for the protection 
of the spinal cord. AVhen the vertebrte are joined they form, with their ligaments, 
the vertebral canal (canalis vertebralis). The laminae are connected to the body 
by means of the pedicles. Their upper and lower borders are rough, for the 
attachment of the lig amenta subfi ava. 

Processes. Spinous Process (processus spinosvs). — The spinous process is 
a rather long, three-sided mass of bone which projects backward from the 
junction of the two laminae and may terminate in a tubercle, and serves for the 
attachment of muscles and ligaments. 

Articular Processes. — The articular processes (zygapophyses), four in number, 
two on each side, spring from the junction of the pedicles with the laminae. Each 
superior process (processus articularis superior) projects upward, its articular sur- 
face (fades articularis superior) being directed more or less backward ; each 
inferior process (processus articularis inferior) projects downward, its articular 
surface (fades articularis inferior) looking more_i>z_l£ss-4©Fward.' 

Transverse Processes (processus transversa) . — The transverse processes, two in 
number, project one at each side from the point where the lamina joins the 
pedicle, between the superior and inferior articular processes. They serve for 
the attachment of muscles and ligaments. 

The Cervical Vertebrae (Vertebrae Cervicales) (Fig. 15). 

The cervical vertebrte are smaller than those in any other region of the spine, 
and may be readily distinguished by the foramen in the transverse process, which 
does not exist in the transverse process of either a thoracic or lumbar vertebra. 

Body. — The body is small, comparatively dense, and broader from side to 
side than from before backward. The anterior and posterior surfaces are flattened 
and of equal depth; the former is placed on a lower level than the latter, and its 
inferior border is prolonged downward, so as to overlap the upper and fore part 
of the vertebra below. Its upper surface is concave transversely, and presents 
a projecting lip on each side; its lower surface is convex from side to side, concave 
from before backward, and presents laterally a shallow concavity which receives 
the corresponding projecting lip of the adjacent vertebra. 

Pedicles. — The pedicles are directed outward and backward, and are attached 
to the body midway between the upper and lower borders; so that the superior 
intervertebral notch is as deep as the inferior, but it is, at the same time, narrower. 

Laminae. — The laminae are narrow, long, thinner above than below, and 
overlap each other,. enclosing the vertebral foramen, which is very large, and of 
a triangular form. 

Processes. Spinous Process. — The spinous process is short, and bifid at the 
extremity, to afi'ord greater extent of surface for the attachment of muscles, the 

' It may, perhaps, be as well to remind the reader that the direction of a surface is determined by that of l 
line drawn at right angles to it. 



50 



SPECIAL ANATOMY OF THE SKELETON 



two divisions being often of unequal size. They increase in length from the fourth 
to the seventh vertebra. 

Articular Processes. — ^The articular processes are flat, oblique, and of an oval 
form ; the -superior are directed backward and upward, the inferior forward and 
downward. 

Transverse Processes. — ^The transverse processes are short, directed down- 
ward, outward, and forward, bifid at their extremity, and marked by a groove 
along the upper surface, which runs downward and outward from the superior 
intervertebral notch and serves for the transmission of one of the cervical nerves. 
They are situated in front of the articular processes and on the outer side of the 
pedicles. The transverse processes are pierced at their bases by a foramen, 
for the transmission of the vertebral artery, vein, and a plexus of sympathetic 
nerves. This foramen is known as the transverse foramen, the costotransverse 
foramen, and the vertebrarterial foramen (J'oramen iransversarium). Each process 
is formed by two roots — the anterior root, sometimes called the costal process, 
arising from the side of the body, and the homologue.of the rib in the thoracic 
region of the column ; the posterior root springs from the junction of the pedicle 
with the lamina, and corresponds to the transverse process in the thoracic region. 



Antenor tubercle of t) ajis- 
verse pi oces!> 

Costotransverse foramen for 
vertebral artery and vein and' 
sympathetic plexu 
Posterior tubercle of 
transverse process 



Costal process 




Ti anil eise process. 

1 



^-^npei lor articular 
pi ocess. 
Infeiior articular pro 



Fig. 15. — Ce^^'ical vertebra. 



It is by the junction of the two that the foramen for the vertebral vessels is formed. 
The extremity of each of these roots form the anterior and posterior tubercles 
of the transverse processes. 

The peculiar vertebrae in the cervical regions are the first, or atlas; the second, 
or axis; and the seventh, or vertebra promlnens. The great modifications in the 
form of the atlas and axis are designed to admit of the nodding and rotatory 
movements of the head. 

Atlas. — ^The atlas (Fig. 16) is so named because it supports the globe of the 
head. The chief peculiarities of this bone are that it has neither body nor spinous 
process. The body is detached from the rest of the bone, and forms the odontoid 
process of the second vertebra; while the parts corresponding to the pedicles 
join in front to form the anterior arch. The atlas is ring-like, and consists of 
an anterior arch, a posterior arch, and two lateral masses. The anterior arch 
(arcus anterior) forms about one-fifth of the ring; its anterior surface is convex, 
and presents about its centre a tubercle (tuberculum anterius) , for the attachment 
of the Long us colli muscle; posteriorly it is concave, and marked by a smooth, 
oval facet {fovea dentis), covered with cartilage, for articulation with the odontoid 
process of the axis. The upper and lower borders give attachment to the anterior 
occipito-atlantal and the anterior atlanto-axial ligaments, which connect it with 



THE CERVICAL VERTEBRAE 



51 



the occipital bone above and the axis below. The posterior arch {arcuH posterior) 
forms about two-fifths of the circumference of the bone; it terminates behind 
in a tubercle (iuberculum postenvs) , which is the rudiment of a spinous process, 
and gives origin to the Rec tus capitis px ^.st.ini.s minor. The diminutive size of 
this process prevents any interference in the movements between the atlas and the 
cranium. The posterior part of the arch presents above and behind a rounded 
edge for the attachment of the posterior occipitoatlantal ligament, while in front 
immediately behind each superior articular process, is a groove {sidcvs arteriae 
■vertebralis) (Fig. 16), sometimes converted into a foramen by a delicate bony 
spiculum, which arches backward from the posterior extremity of the superior 
articular process. These grooves represent the superior intervertebral notches, 
and are peculiar in that they are situated behind the articular processes, instead 
of in front of them, as in the other vertebra;. They serve for the transmission of 
the vertebral artery, which, ascending through the foramen in the transverse 
process, winds around the lateral mass in a backward and inward direction. 
They also transmit the suboccipital (first spinal) nerve. On the under surface of 
the posterior arch, in the same situation, are two other grooves, placed behind 
the lateral, masses, and representing the inferior intervertebral notches of other 
vertebrae. They are much less marked than the superior. The lower border 

*" Dtaqram of section of odontoid, 

pt oce^s 

Diaqi am of section of 
t)ansieise hgamenL 

Foramen for 
vertebral artery. 




Groove for vertebral artery 
and 1st cermcal nerve. 



Endhnentary spinous process. 

Fig. 16. — First cervical vertebra, 



i\,_J,^\ CoJ^^'"^ j^aWti'-"-^ Vv^C^ftv 



also gives attachment to the posterior atlanto-axial ligament, which connects it 
with the axis. The lateral masses {massae laterales) are the most bulky and solid 
parts of the atlas, in order to support the weight of the head; they present two 
articulating surfaces above and two below. Each represents one-fifth of the ring. 
The superior articular surface {fovea articularis superior) of each is of large size, oval, 
concave, and approaches its companion in front, but diverges from it behind ; it 
is directed upward, inward, and a little backward, forming a kind of cup for the 
corresponding condyle of the occipital bone. The two processes are admirably 
adapted to the nodding movements of the head. Not infrequently they are par- 
tially subdivided by a more or less deep indentation, which encroaches upon 
each lateral margin. Each inferior articular process (fades articularis inferior) is 
circular in form, flattened or slightly concave, and directed downward and inward, 
articulating with the axis. The inferior processes permit the rotatory movements. 
Just below the inner margin of each superior articular surface is a small tubercle, 
for the attachment of the transverse ligament, which, stretching across the ring 
of the atlas, divides it into two unequal parts or arches; the anterior or smaller 
segment receiving the odontoid process of the axis, the posterior allowing the 
transmission of the spinal cord and its membranes. This part of the vertebral 
canal is of considerable size, to aft'ord space for the spinal cord; and hence lateral 



52 SPECIAL ANATOMY OF THE SKELETON 

displacement of the atlas may occur without compression of this structure. The 
transverse processes are of large size, project directly outward and downward 
from the lateral masses, and serve for the attachment of special muscles which 
assist in rotating the head. They are long, not bifid, and perforated at their 
bases by a canal for the vertebral artery, which is directed from below, upward, 
and backward. 

Axis. — The axis (epistropheus) (Fig. 17) is the pivot upon which the first 
vertebra, carrying the head, rotates. The most distinctive character of this bone 
is the strong, prominent process, tooth-like in form, which rises perpendicularly 
from the upper surface of the body. The body is deeper in front than behind, 
and prolonged downward anteriorly so as to overlap the upper and fore part of 
the next vertebra. It presents in front a median longitudinal ridge, separating 
two lateral depressions, for the attachment of the Longus colli muscles of either 
side. The odontoid process presents two articulating surfaces covered with 
cartilage; one in front, of an oval form, for articulation with the atlas (fades 
articularis anterior) ; another behind (fades articularis posterior) , for the transverse 

Odontoidjprocess, 

Bough surface for checTc ligaments. — ,^i^, 

■■^i^s it.,^ 1 j^Yfii^niar surface for 
atlas. 
Articular surf ace for ti ansierse ligament ^^i X\ i 




Spinous process.-^^i^ 'W'MW iJ ■/ 

I Transtiei »e process. 
Inferior articular process. 
Fig. 17. — Second c-ervical vertebra, or a.xis. 

ligament — the latter frequently encroaching on the sides of the process. The 
apex is pointed, and gives attachment to the middle odontoid ligament. Below 
the apex the process is somewhat enlarged, and presents on either side a rough 
impression for the attachment of the lateral fasciculi of the odontoid or check 
ligaments, which connect it to the occipital bone; the base of the process, wliere 
it is attached to the body, is constricted, so as to prevent displacement from the 
transverse ligament, which binds it in this situation to the anterior arch of the 
atlas. The pedicles are broad and strong, especially their anterior extremities, 
which coalesce with the sides of the body and the root of the odontoid process. 
The laminas are thick and strong, and the spinal foramen large, but smaller 
than that of the atlas. The transverse processes are very small, not l^ifid, and each 
is perforated by the foramen for the vertebral artery, wErdi is directed obliquely 
upward and outward. The superior articular siu-faces (fades articulares superiores) 
are circular, slightly convex, directed upward and outward, and are peculiar 
in being supported on the body, pedicles, and transverse processes. The inferior 
articular surfaces (fades articulares inferiores) have the same direction as those 
of the other cervical vertebree. The superior intervertebral notches are very 
shallow, and lie behind the articular processes; the inferior in front of them, 
as in the other cervical vertebrae. The spinous process is of large size, very strong, 
deeply channelled on its under surface, and presents a bifid, tubercular extremity' 
for the attachment of muscles which serve to rotate the headTipon the spine. 



THE THORACIC VEllTEBRjE 



53 



Seventh Cervical (Fig. 18).— The most distinctive character of this vcrtel)ra 
is the existence of a very long and prominent spinous process, hence the name, 
vertebra prominens. This pro- 
cess is thick, nearly horizontal 
in direction, not bifurcated, and 
gives attachment to the lower 
end of the ligamentum nuchae. 
The transverse process is usually 
of large size, its posterior tuber- 
cles are large and prominent, 
while the anterior are small and 
faintly marked; its upper surface 
has usually a shallow groove, and 
it seldom presents more than a 
trace of__bifurcation at its ex- 
tremity. The foramen in the 
transverse process is sometimes 
as large as in the other cervical 
vertebras, but is usually smaller 
on one or both sides, and is 
sometimes absent. Usually the 
vertebral artery and vein pass in 
front of the transverse process, 
but occasionally it is traversed on both sides by these vessels, or the left one 
alone may give passage to them. Occasionally the anterior root of the trans- 
verse process exists as a separate bone, and attains a large size. It is then 
called' a cervical rib. 




The Thoracic Vertebrae (Vertebrae Thoracales). 

The thoracic vertebrae are intermediate in size between those in the cervical and 
those in the lumbar region, and increase in size from above downward, the upper 
vertebrse in this segment of the column being much smaller than those in the 
lower part. A thoracic vertebra may be at once recognized by the presence on 
each side of the body of one or more facets or half-facets for the heads of the ribs. 

Bodies. — The bodies of the thoracic vertebrae resemble those in the cervical 
and lumbar regions at the respective ends of this portion of the vertebral column, 
but in the middle of the thoracic region their form is very characteristic, being 
heart-shaped, and as broad in the antero-posterior as in the lateral direction. 
They are thicker behind than in front, flat above and below, convex and prominent 
in front, deeply concave behind, slightly constricted in front and at the sides, 
and marked on each side, near the root of the pedicle, by two demi-facets, one 
above, the other below (fovea costalis superior et inferior). These are covered by 
cartilage in the recent state, and, when articulated with the adjoining vertebrse, 
form, with the intervening fibrocartilage, oval surfaces for the reception of the 
heads of the corresponding ribs. 

Pedicles. — The pedicles are directed backward, and the inferior intervertebral 
notches are of large size, and deeper than in any other region of the spine. 

Laminae. — The laminae are broad, thick, and imbricated — that is to say, 
overlapping one another like tiles on a roof. The vertebral foramen is small, 
and of a circidar form. 

Processes. — Spinous Processes. — Each spinous process is long, triangular on 
transverse section, directed obliquely downward, and terminates in a tubercular 



54 



SPECIAL ANATOMY OF THE SKELETON 



extremity. They overlap one another from the fifth to the eighth vertebra, but 
are less oblique in direction above and below. 

Articular Processes. — The articular processes are flat, nearly vertical in direction, 
and project from the upper and lower part of the pedicles; the superior being 
directed backward and slightly outward and upward, the inferior forward and a 
little inward and downward. 



Superior articulai pt ocesi 



Facet for tubercle of 




F-.o. 19.— A th 



Transverse Processes. — The transverse processes arise from the same parts 
of the arch as the posterior roots of the transverse processes in the neck, and 
are situated behind the articular processes and pedicles; they are thick, strong, 
and of great length, directed obliquely backward and outward, presenting a 
clubbed extremity, and having on its anterior part near its tip a small concave 
surface, for articulation with the tubercle of a rib (fovea costalis transversalis). 
Besides the articular facet for the rib, three indistinct tubercles may be seen 
arising from the transverse processes — one at the upper border, one at the lower 
border, and one externally. In man they are of comparatively small size, and 
serve only for the attachment of muscles. But in some animals they attain con- 
siderable magnitude, either for the purpose of more closely connecting the segments 
of this portion of the vertebral column or for muscular and ligamentous attachment. 

The peculiar thoracic vertebrse are the first, ninth, tenth, eleventh, and twelfth 
(Fig. 20). 

First Thoracic Vertebra. — The first thoracic vertebra presents, on each side 
of the body, a sin^e^ntire articular facet for the head of the first rib and a demi- 
facet for the upper half of the second. The body is like that of a cervical vertebra, 
being broad transversely, its upper surface is concave, and lipped, pneach side. 
The articular surfaces are oblique,"and the spinous process thick, long, and almost 
horizontal. 

Ninth Thoracic Vertebra. — ^The ninth thoracic vertebra has no demi-facet 
below. In some subjects, however, the ninth has two demi-facets on eacTi side; 
when this occurs the tenth has only a demi-facet at the upper part. 

Tenth Thoracic Vertebra. — The tenth thoracic vertebra has (except in the 
case just mentioned) an entire articular facet on each side, above, which is partly 



THE THORACIC VERTEBRAE 

placed on the outer jurface-of-the-pedicle. It has no demi-facet below, 
times it has no facet on its transverse process. 



55 

Some- 




( An entire facet above; 
\ a demi-facet below. 



—A demi-facet atiove. 



One entire facet. 



entire facet. 



J. No facet on rudimentary 
(_ transverse process. 



entire facet. 
No facet on trans- 
verse process. 
Inferior articidat 



Fig. 20.— Peculi; 



Eleventh Thoracic Vertebra. — The body of this vertebra approaches in its 
form and size that of the lumbar vertebra. The articular facets for the heads 
of the ribs, one on each side, are of large size, and placed chiefly on the pedicles, 
which^are'thicker and stronger in this and the next vertebra than in any other 
part of the thoracic region. The spinous process is short, and nearly horizpntal 
in direction. The transverse processes are very short, Tubercular at their extrem- 
ities, and have no articiilar facets for the tubercles o? tbe ribs. 

Twelfth Thoracic Vertetra. — The twelfth thoracic vertebra has the same 
general characters as the eleventh, but may be distinguished from it by the in- 



56 



SPECIAL ANATOMY OF THE SKELETON 



ferior articular processes being convex and turned outward, like those of the 
lumbar vertebrae; and by the fact that this vertebra resembles the lumbar vertebrae 
in the general form of the body, laminae, and spinous process; and by the trans- 
verse processes being shorter, and marked by three elevations, the superior, 
inferior, and external tubercles, which correspond to the mammillary, accessory, 
and transverse processes of the lumbar vertebrae. There is no facet on its 
transverse process for the twelfth rib. 



The Lumbar Vertebrae (Vertebrae Lumbales) (Fig. 21). 

The lumbar vertebrae are the largest segments of the vertebral column, and can 
at once be distinguished by the absence of the foramen in the transverse process, 
the characteristic point of the cervical vertebrae, and by the absence of any articu- 
lating facet on the side of the body, the distinguishing mark of the thoracic 
vertebrae. 



Superioi a)ticula> pi ocas 




Fig. 21. — Lumbar vertebra. 

Body. — ^The body is large, and has a greater diameter from side to side than 
from before backward, slightly thicker in front than behind, flattened or slightly 
concave above and below, concave behind, and deeply constricted in front and at 
the sides, presenting prominent margins, which afford a broad surface for the 
support of the superincumbent weight. 

Pedicles. — The pedicles are very strong, directed backward from the upper 
part of the bodies; consequently, the inferior intervertebral notches are of con- 
siderable depth. 

Laminaj.- The laminae are broad, short, and strong, and the vertebral foramen 
triangular, larger than in the thoracic, smaller than in the cervical, region. 

Processes. Spinous Processes. — The spinous processes are thick and broad, 
somewhat quadrilateral, horizontal in direction, thicker below than above, and 
terminating in a rough, uneven border. 

Articular Processes. — The superior articular processes are concave, and look 
backward and inward; the inferior are convex, and look forward and outward; 
the former are separated by a much wider interval than the latter, embracing 
the lower articulating processes of the vertebra above. 

Transverse Processes. — The transverse processes are long, slender, directed 
transversely outward in the upper three lumbar vertebrae, slanting a little upward 
in the lower two. They are situated in front of the articular processes, instead 
of behind them, as in the thoracic vertebrae, and are homologous with the ribs. Of 
the three tubercles noticed in connection with the transverse processes of the 



THE LUuMBAB VERTEBRA 



57 



twelfth thoracic vertebra, the superior one on each side becomes connected in tliis 
region witli the back part of the superior articular process, and has received tiie 
name of mammillary process {processus mamillaris) ; the inferior is represented 
by a small process pointing downward, situated at the back part of the base of 
the transverse process, and called the accessory process (processus accessorius); 
these are the true transverse processes, which are rudimentary in this region of 
the spine. The external one, the so-called transverse process, is the homoloo-ue 
of the rib, and constitutes the costal process (processus costarius) (Fig. 22). 
Although in man the costal processes are comparatively small, in some animals 
they attain considerable size, and serve to lock the vertebrte more closely together. 



Inferior articulaT 
process 



Transverse process 



Superior articular 
process 




StNf^ /«*V^P a Mammillary process 
\\\/ MvA.j^ S^^W.///Z^^ ^ ^ Accessory process- 



Fig. 22. — Lumbar vertebra, viewed obliquely. 



i'ifth Lumbar Vertebra. — The fifth lumbar vertebra is characterized by 
haing the body much thicker in front than behind, which accords with the promi- 
nence of the sacrovertebral articulation; by the smaller size of its spinous process; 
by t\e wide interval between the inferior articulating processes ; and by the greater 
size \nd thickness of its transverse processes, which spring from the body as well 
as fr^ the pedicles. 

Attahment of Muscles. — To the Atlas are attached nine pairs: the Longus colli, Rectus 
capitis ntieus minor, Rectus lateralis, Obliquus capitis superior and inferior, Splenius colli, 
Levator\nguli scapulae. First Intertransverse, and Rectus capitis posticus minor. 

To th* Axis are attached eleven pairs: the Longus colli. Levator anguli scapulae, Splenius 
colli, Scajnus medius, Transversalis colli, Intertransversales, Obliquus capitis inferior. Rectus 
capitis poiicus major, Semispinalis colli, Multifidus spinae, Interspinales. 

To the -emaining vertebrae, generally, are attached thirty-five pairs and a single muscle: 
anteriorly, he Rectus capitis anticus major, Longus colli. Scalenus anticus, medius, and posticus. 
Psoas magiis and parvus, Quadratus lumborum, Diaphragm, Obliquus abdominis internus, 
and Trans\rsalis abdominis; posteriorly, the Trapezius, Latissimus dorsi. Levator anguli 
scapulae, Rtimboideus major and minor, Serratus posticus superior and inferior, Splenius, 
Erector spirip, Iliocostalis, Longissimus dorsi. Spinalis dorsi, Cervicalis ascendens, Trans- 
versalis colli,Trachelomastoid, Complexus, Biventer cervicis, Semispinalis dorsi and colli, 
Multifidus spine, Rotatores spinae, Interspinales, Supraspinales, Intertransversales, Levatores 
costarum. \ 



58 



SPECIAL ANATOMY OF THE SKELETON 



The Sacral and Coccygeal Vertebrae. 

The sacral and coccygeal vertebrae consist, at an early period of life, of nine 
separate pieces, which are united in the adult so as to form two bones, five enter- 
ing into the formation of the sacrum, four into that of the coccyx. Occasionally, 
the coccyx consists of five bones. ^ 

Sacrum (os sacrum). — The sacrum is a large, triangular bone (Fig. 23), 
situated at the lower part of the vertebral column, and at the upper and back 
part of the pelvic cavity, where it is inserted like a wedge between the two in- 
nominate bones; its upper part or base articulating with the last lumbar vertebra. 




Fig. 23. — Sacrum, anterior surface. 



its apex with the coccyx. It is composed of five segments of bone. The acrum 
is curved upon itself, and placed very obliquely, its upper extremity prqecting 
forward, and forming, with the last lumbar vertebra, a very prominent angle, 
called the promontory (promontorium), or sacrovertebral angle; while its central 
part is directed backward, so as to give increased capacity to the pelvi cavity. 
It presents for examination an anterior and posterior surface, two lateraburfaces, 
a base, an apex, and a central Canal. 

Surfaces. Anterior or Pelvic Surface (fades pelvina). — The antervr surface 
is concave from above downward, and slightly so from side to sid- In the 
middle are seen four transverse ridges (Imeae transversae) , indicating fle original 
division of the bone into five separate pieces. The portions of bonentervening 



^ Sir George Humphry describes this 



ual composition of the coccyx. " On the Slie'fo 



THE SACRAL AND COCCTGEAL VERTEBRA 



59 



between the ridges correspoiui to the bodies of the vertebrae. The body of the first 
segment is of large size, and in form resembles that of a luml)ar vertebra; the 
succeeding ones diminish in size from above downward, are flattened from before 
backward, and curved so as to accommodate themselves to the form of the sacrum 
being concave in front, convex behind. At each end of the ridges above men- 
tioned are seen the anterior sacral foramina (foramina sacralia anteriora), analoo-ous • 
to the intervertebral foramina, four in number on each side, somewhat circular 
in form, diminishing in size from above downward, and directed outward and 
forward; they transmit the anterior branches of the sacral nerves and the lateral 
sacral arteries. External to these fora- 
mina is the lateral mass (pars lateralis), 
consisting at an early period of life of 
separate segments ; these become blended, 
in the adult, vi^ith the bodies, with each 
other, and with the posterior transverse 
processes. Each lateral mass is traversed 
by four broad, shallow grooves, which 
lodge the anterior divisions of the sacral 
nerves as they pass outward, the grooves 
being separated by prominent ridges of 
bone, which give attachment to the slips 
of the Pyriformis muscle. 

If a vertical section is made through 
the centre of the sacrum (Fig. 24), the 
bodies are seen to be united at their cir- 
cumference by bone, a wide interval being 
left centrally, which, in the recent state, 
is filled by intervertebral substance. 
In some bones this union is more com- 
plete between the lower segments than 
between the upper ones. 

Posterior or Dorsal Suriace (fades dor- 
salis). — The posterior suriace (Fig. 25) 
is convex and much narrower than the 
anterior. In the middle line are three 
or four tubercles, which represent the rudi- 
mentary spinous processes of the sacral 
vertebrae. Of these tubercles, the first 
is usually prominent, and perfectly dis- 
tinct from the rest; the second and 
third are either separate or united into a 
tubercular ridge (crista sacralis media), which diminishes in size from above 
downward; the fourth usually, and the fifth always, remaining undeveloped; 
being undeveloped, in this situation the lower end of the sacral canal is exposed. 
The gap is called the hiatus sacralis. External to the spinous processes on each 
side are the laminje, broad and well marked in the first three pieces; sometimes 
the fourth, and generally the fifth. External to the laminae is a linear series of 
indistinct tubercles representing the articular processes (crisfac sacrales artiat- 
lares); the upper pair are large, well developed, and correspond in shape and 
direction to the superior articulating processes of a lumbar vertebra; the second 
and third are small; the fourth and fifth (usually blended together) are situated 
on each side of the exposed part of the sacral canal and form downward project- 
ing processes^ the sacral cornua, and are connected to the cornua of the coccyx. 




-Vertical section of the sacrum. 



60 



SPECIAL ANATOMY OF THE SKELETON 



External to the articular processes are the four posterior sacral foramina {foram- 
ina sacralia posteriora) ; they are smaller in size and less regular in form than the 
anterior, and transmit the posterior branches of the sacral nerves. On the outer 
side of the posterior sacral foramina is a series of tubercles, the rudimentary 
transverse processes of the sacral vertebrse (cristae sacrales laterales). The 
first pair of transverse tubercles are large, very distinct, and correspond with 
each superior angle of the bone; they, together with the second pair, which are 
of small size, give attachment to the horizontal part of the posterior sacro- 
iliac ligament; the third gives attachment to the oblique fasciculi of the pos- 
terior sacroiliac ligaments; and the fourth and fifth to the great sacrosciatic 
ligaments. The interspace between the spinous and transverse processes on 
the back of the sacrum presents a wide, shallow concavity, called the sacral 




Erector spinse. 



|H— ia^iSSiOTua dorsl. 



] — • Erector spinas. 



Upper half of fifth 
lor sacral foramen. 



Fig. 25. — Sacrum, dorsolateral view. 



groove; it is continuous above with the vertebral groove, and lodges the origin 
of the Multifidus spinae. 

Lateral Surface. — ^The lateral surface, broad above, becomes narrowed into a 
thin edge below. Its upper half presents in front a broad, ear-shaped surface for 
articulation with the ilium. This is called the auricular surface [fades auricularii), 
and in the fresh state is coated with fibrocartilage. It is bounded posteriorly 
by deep and uneven impressions, for the attachment of the posterior sacroiliac 
ligaments. The chief prominence is called the tuberosity {tuberositas sacralis). 
The lower half is thin and sharp, and terminates in a projection called the inferior 
lateral angle; below this angle is a notch, which is converted into a foramen by 
articulation with the transverse process of the upper piece of the coccyx, and 



THE SACRAL AND COCCYGEAL VERTEBRA 01 

transmits the anterior division of the fifth sacral nerve. This lower, sharp border 
gives attachment to the greater and lesser sacrosciatic ligaments, and to some 
fibres of the Gluteus maximus posteriorly, and to the Coccygeus in front. 

Base (basis oss. sacri). — The base of the sacrum, which is broad and expanded, 
is directed upward and forward. In the middle is seen a large oval articular 
surface, which is connected with the under surface of the body of the last lumbar 
vertebra by a fibrocartilaginous disk. It is bounded behind by the large, tri- 
angular orifice of the sacral canal. The orifice is formed behind by the laminae 
and spinous process of the first sacral vertebra: the superior articular processes 
project from it on each side; they are oval, concave, directed backward and inward, 
like the superior articular processes of a lumbar vertebra; and in front of each 
articular process is an intervertebral notch, which forms the lower part of the 
foramen between the last lumbar and first sacral vertebra. Lastly, on each side 
of the large oval articular plate is a broad and flat triangular surface of bone, 
which extends outward, supports the Psoas magnus muscle and lumbosacral 
cord, and is continuous on each side with the iliac fossa. This is called the ala of 
the sacrum (ala sacralis), and gives attachment to a few of the fibres of the Iliacus 
muscle. The posterior part of the ala represents the transverse process of the 
first sacral segment. 

Apex (apex OSS. sacri). — The apex, directed downward and slightly forward, 
presents a small, oval, concave surface for articulation with the coccyx. ^ 

The Sacral Canal (canalis sacralis) runs throughout the greater part of 
the bone; it is large and triangular in form above, small and flattened, from 
before backward, below. In this situation its posterior wall is incomplete, from 
the non-development of the laminae and spinous processes (hiafus sacralis). 
It lodges the sacral nerves, and is perforated by the anterior and posterior sacral 
foramina, through which these pass out. I^ constitutes the sacral continuation 
of the vertebral canal (Fig. 24). 

Diflerences in the Sacrum of the Male and Female.— The sacrum in the female 
is shorter and wider than in the male; the lower half forms a greater angle with the upper, the 
upper half of the bone being nearly straight, the lower half presenting the greatest amount 
of curvature. The bone is also directed more obliquely backward, which increases the size 
of the pelvic cavity; but the sacrovertebral angle projects less. In the male the curvature is 
more evenly distributed over the whole length of the bone, and is altogether greater than in the 
female. 

Variations. — This bone, in some cases, consists of six pieces; occasionally the number is 
reduced to four. Sometimes the bodies of the first and second segments are not joined or the 
laminse and spinous processes have not coalesced. Occasionally the upper pair of transverse 
tubercles are not joined to the rest of the bone on one or both sides; and, lastly, the sacral canal 
may be open for nearly the lower half of the bone, in consequence of the imperfect development 
of the laminae and spinous processes. The sacrum, also, varies considerably with respect to 
its degree of curvature. 

Articulations. — With /our bones: the last hmibar vertebra, coccyx, and the two innominate 
bones. 

Attachment of Muscles. — To eight pairs: in front, the Pyriformis and Coccygeus, and a 
portion of the Iliacus to the base of the bone; behind, the Gluteus maximus, Latissimus dorsi, 
Multifidus spinae, and Erector spinae, and sometimes the Extensor coccygis. 

Coccyx (os coccygis). — ^The coccyx (Fig. 26) is usually formed of four small 
segments of bone, the most rudimentary parts of the vertebral column (vertebrae 
coccygeae). In each of the first three segments may be traced a rudimentary 
body, articular and transverse processes; the last piece (sometimes the third) 
is a mere nodule of bone, without distinct processes. All the segments are desti- 
tute of pedicles, laminae, and spinous processes, and consequently of interverte- 
bral foramina and vertebral canal. The first segment is the largest; it resembles 
the lowermost sacral vertebra, and often exists as a separate piece; the last three, 



62 



SPECIAL ANATOMY OF THE SKELETON 



diminishing in size from above downward, are usually blended to form a single 
bone. The gradual diminution in the size of the pieces gives this bone a tri- 
angular form, the base of the triangle joining the apex of the sacrum. It presents 
for examination an anterior and posterior surface, two borders, a base, and an 
apex. 




■'Tor ►" 

Antunor surface. 




Posterior surface. 



Fig. 26. — Coccyx, 



Surfaces. Anterior Surface. — The anterior surface is slightly concave and 
marked with three transverse grooves, indicating the points of junction of the differ- 
ent pieces. It has attached to it the anterior sacrococcygeal ligament and Levator 
ani muscle, and supports the lower end of the rectum. 

Posterior Surface. — The posterior surface is convex, marked by transverse 
grooves similar to those on the anterior surface; and presents on each side a lineal 
row of tubercles, the rudimentary articular processes of the coccygeal vertebrse. 
Of these, the superior pair are large, and are called the cornua of the coccjrx (cornua 
coccygea) ; they project upward, and articulate with the cornua of the sacrum, the 
junction between these two bones completing the fifth posterior sacral foramen for 
the transmission of the posterior division of the fifth sacral nerve. 

Borders. — The lateral borders are thin, and present a series of small emi- 
nences, which represent the transverse processes of the coccygeal vertebrae. Of 
these, the first on each side is the largest, flattened from before backward, and often 
ascends to join the lower part of the thin lateral edge of the sacrum, thus completing 
the fifth anterior sacral foramen for the transmission of the anterior division 
of the fifth sacral nerve; the others diminish in size from above downward, and 
are often wanting. The borders of the coccyx are narrow, and give attachment on 
each side to the sacrosciatic ligaments, to the Coccygeus muscles in front of the 
ligaments, and to the Gluteus maximus behind them. 

Base. — The base presents an oval surface for articulation with the sacrum. 

Apex. — ^The apex is rounded, and has attached to it the tendon of the external 
Sphincter muscle. It is occasionally bifid, and sometimes deflected to one or 
the other side. 



Articulation.— With the sacrum. 

Attachment of Muscles. — To four pairs and one single muscle: on either side, the Coccygeus; 
behind, the Gluteus maximus and Extensor coccygis, when present; at the apex, the Sphincter 
ani; and in front, the Levator ani. 

Structure of the Vertebrae. — The body is composed of light, spongy, cancellous tissue, 
having a thin coating of compact tissue on its external surface perforated by numerous orifices 
of various sizes for the passage of vessels; its interior is traversed by one or two large canals 
(for the transmission of veins) , which converge toward a single large, irregular aperture or several 
small apertures at the posterior part of the body of each bone. The arch and processes pro- 



THE SACRAL AND COCCYGEAL VERTELU^K 63 

jecting from it have, on the contrary, an exceedingly thick covering of compact tissue (Fig 
27). 

The sacrum and coccyx consist mainly of spongy bone covered by a thin layer of compact 
bone. 




Fig. 27. — Bony structure of a lumbar vertebra. (Poirier and Charpy.) 

Development. — Each vertebra is formed of four primary centres of ossification (Fig. 28), 
one for each lamina and its processes, and two for the body.' Ossification commences in the 
laminae about the sixth week of fetal life, in the situation where the transverse processes afterw ard 
project, the ossific granules spreading backward to the spine, forward into the pedicles, and out- 
ward into the transverse and articular processes. Ossification in the body commences in. the 
middle of the cartilage about the eighth week by two closely approximated centres, which speedily 
coalesce to form one central ossific point. According to some authors, ossification commences 
in the laminie only in the upper vertebrs; — i. e., in the cervical and upper thoracic. The first 
ossific points in the lower vertebrae are those which are to form the body, the osseous centres 
for the laminse appearing at a subsequent period. At birth these three pieces are entirely sepa- 
rate. During the first year the laminae become united behind, the union taking place first in 
the lumbar vertebrae and then extending upward through the thoracic and lower cervical verte- 
bras. About the third year the body is joined to the arch on each side in such a manner that the 
body is formed from the three original centres of ossification, the amount contributed by the 
pedicles increasing in extent from below upward. Thus, the bodies of the sacral vertebra are 
formed almost entirely from the central nuclei; the bodies of the lumbar are formed laterally 
and behind by the pedicles; in the thoracic region the pedicles advance as far forward as the 
articular depressions for the head of the ribs, forming these cavities of reception ; and in the neck 
the lateral portions of the bodies are formed entirely by the advance of the pedicles. The line 
along which union takes place between the body and the neural arch is named neurocentral 
suture. Before puberty no other changes occur, excepting a gradual increase in the gro\\th - 
of these primary centres; the upper and under surfaces of the bodies and the ends of the transverse 
and spinous processes being tipped with cartilage, in which ossific granules are not as yet de- 
posited. At sixteen years (Fig. 30) three secondary centres appear, one for the tip of each trans- 
verse process, and one for the extremity of the spinous process. In some of the lumbar vertebrae, 
especially the first, second, and third, a second ossifying centre appears at the base of the spinous 
process. At twenty-one years (Fig. 29) a thin, circular, epiphyseal plate of bone is formed 
in the layer of cartilage situated on the upper and under surfaces of the body, the former being 
the thicker of the two. These represent two additional secondary centres of ossification. \\\ 
these become joined, and the bone is completely formed between the twenty-fifth and thirtieth 
year of life. 

Exceptions to this mode of development occur in the first, second, and seventh cervical, and 
in the vertebrae of the lumbar region. 

Atlas (Fig. 31).— The number of centres of ossification of the atlas is quite variable. It 
may be developed from iwo, three, four, or five centres. The most frequent method is from 
three centres. Two of these are destined for the two lateral or neural masses, the ossification 
of which commences about the seventh week near the articular processes, and extends backward; 
these portions of bone are separated from one another behind, at birth, by a narrow interval 
filled in with cartilage. Between the third and fourth vears they unite either directly or through 
the medium of a separate centre developed in the cartilage in the median line. The anterior 

> By many observers it is asserted that the bodies of the vertebra are developed from a single centre which 
speedily becomes bilobed, so as to give the appearance of two nuclei; but that there are two centres, at all eienta 
sometimes, is evidenced by the facts that the t-s-o h.alves of the body of the vertebra may remam distmct 
throughout life, and be separated by a fissure through which a protrusion of the spinal membrane may take 
place, constituting an anterior spina bijida. 



64 



SPECIAL ANATOMY OF THE SKELETON 



arch, at birth, is altogether cartilaginous, and in this a separate nucleus appears about the end 
of the first year after birth, and, extending laterally, joins the neural processes in front of the pedi- 
cles. Sometimes there are two centres developed in the cartilage, one on either side of the median 

line, which join to form a single mass. 



By If primary centres. 

1 fui hud;/ (Sih week). 




1 for each lamina (6th weeh). 
Fig. 28. — Development of a vertebra. 



I plates. 




1 for upper surface "i 
of body, 



■ 21 year^ 



,1 for nn.der surface 
of body. 



By 4 secondary centres. 




1 for each trans- 
verse process, 
16 years. 



2 (sometimes 1) for spinous process (16 years). 
Fig. 30 



By S ccnir 




anterior arch (1st year), 

not c/mstant. 



before birth. 



6th month. 

1 for each lateral mass. 

1 for body (4fh month). 
1 'for under surface of 

body. 
Axis. 




jnr tubeicles on supenoi aiticulai process. 
Fig. 33. — Lumbar vertebra. 



And occasionally there is no separate 
centre, but the anterior arch is formed 
by the gradual extension forward and 
ultimate junction of the two neural pro- 
cesses. 

Axis. — The axis (Fig. 32) is developed 
by seven centres, five primarij and tico 
secondary. The body and arch of this 
bone are formed in the same manner as 
the corresponding parts in the other 
vertebrae: one centre (or two, which 
speedily coalesce) for the lower part of 
the body, and one for each lamina. 
The centres for the laminre appear 
about the seventh or eighth week, that 
for the body about the fourth month. 
The odontoid process consists originally 
of an extension upward of the cartilagi- 
nous mass in which the lower part of the 
body is formed. At about the sixth 
month of fetal life two centres make 
their appearance in the base of this pro- 
cess; they are placed laterally, and join 
before birth to form a conical bilobed 
mass deeply cleft above; the interval be- 
tween the cleft and the summit of the 
process is formed by a wedge-shaped 
piece of cartilage, the base of the process 
being separated from the body by a car- 
tilaginous interval, which gradually be- 
comes ossified at its circumference, but 
remains cartilaginous in its centre until 
advanced age. Finally, the apex of the 
odontoid process has a separate (second- 
ary) centre, which appears in the second 
year and joins about the twelfth year. 
In addition to these there is a secondary 
centre for a thin epiphyseal plate on the 
under surface of the body of the bone. 

Seventh Cervical. — The anterior or 
costal part of the transverse process of the 
seventh cervical is developed from a 
separate osseous centre at about the 
sixth month of fetal life, and joijis the 
body and posterior division of the trans- 
verse process between the fifth and sixth 
years.. In rare instances this process 
continues as a separate piece, and, be- 
coming lengthened outward, constitutes 
what is known as a cervical rib. This 
separate ossific centre for the costal 
process has also been found in the fourth, 
fifth, and sixth cervical vertebras. 

Lumbar Vertebree. — The hmibai- 
vertebrre (Fig. 33) have two additional 
centres (besides those peculiar to the 
vertebrae generally) for the mamraillary 
tubercles, which project from the back 
part of the superior articular processes. 
The transverse process of the first 
lumbar is sometimes developed as a 
separate piece, which ma}' remain per- 



THE SACRAL AND COCCYGEAL VETlTEBRjE 



60 



manently unconnected with the remaining portion of the bone, thus forming a himhar rib a 

peculiarity. 

The sacrum, formed by the union of five vertebrae, has thirty-five centres of ossification. 

The bodies of the sacral vertebrae have each three ossific centres — one for the central part 
and one for the epiphyseal plates on its upper and under surface. Occasionally the iirimary 
centres for the bodies of the first and second piece of the sacrum are double. The arch of each 
sacral vertebra is developed from two centres, one for each lamina. These unite with each other 
behind, and subsequently join the body. 

The lateral masses have six additional centres, two for each of the first three vertebrte. These 
centres, representing costal elements, make their appearance above and to the outer side of 
the anterior sacral foramina (Fio;. 34), and are developed into separate segments (Fig. 3.5); 
they are subsequently blended with each other, and with the bodies and transverse processes 
to form the lateral mass. 

Lastly, each lateral surface of the sacrum is developed from two epiphyseal plates (Fig. 36) — 
one for the auricular surface, and one for the remaining part of the thin lateral edge of the bone. 



Additional cetitte^ 
for the /i)s( time piei 



Two epiphysial lamines 
for each lateral surface/'^ 




Fig. 34. — Development of the sacrum. 



Period of Development.— At about the eighth or ninth week of fetal life ossification of the 
central part of the bodies of the first three vertebrae commences, and between the fifth and 
eighth months in the last two. Between the si.xth and eighth months ossification of the lamina 
takes place; and at about the same period the centres for the lateral masses for the first three sacral 
vertebrfe make their appearance. The period at which the arch becomes completed by the junc- 
tion of the laminae with the bodies in 
front and with each other behind varies 
in different segments. The junction 
between the laminae and the bodies takes 
place first in the lower vertebrae as early 
as the second year, but is not effected in 
the uppermost until the fifth or sixth year. 
About the sixteenth year the epiphyses 
for the upper and under surfaces of the 
bodies are formed, and between the 
eighteenth and twentieth years those for 
each lateral surface of the sacrum make 
their appearance. The bodies of the 
sacral vertebrae are, during early life, 

separated from each other by intervertebral disks. At about the eighteenth year the two 
lowest segments become joined by ossification extending through the disk. This process 
gradually extends upward until all the segments become united, and the bone is completely 
formed from the twenty-fifth to the thirtieth year of life. 

The coccyx is developed from four centres, one for each piece. Occasionally one of the first 
three pieces of this bone is developed from two centres, placed side by side. The ossific nuclei 
make their appearance in the following order: In the first segment, between the first and fourth 
years; in the second piece, at from five to ten years; in the third, from ten to fifteen years; inthe 
fourth from fourteen to twenty years. As age advances these various segments become^ united 
with each other from below upward, the union between the first and second segments being fre- 
quently delayed until after the age of twenty-five or thirty. At a late period of life, especially in 
females, the coccyx often becomes ankylosed to the end of the sacrum. 




'arly stage. 



66 



SPECIAL ANATOMY OF THE SKELETON 




Coccyx. 
Fig, 38. — Lateral view of the vertebral column. 



The Vertebral Column as a Whole. 

The vertebral column (columna verte- 
bralis), formed by the interarticulatioii of 
the vertebrae, is situated in the median line, 
in the posterior part of the trunk; its average 
length is about two feet two or three inches 
(65 to 67.5 cm.), measuring along the curved 
anterior surface of the column. Of this 
length, the cervical part measures about 
five, the thoracic about eleven, the lumbar 
about seven inches, and the sacrum and 
coccyx the remainder. The female column 
is about one inch less than that of the male. 

Viewed laterally (Fig. 38), the spinal 
column presents several curves which cor- 
respond to the different regions of the 
column, and are called cervical, thoracic, 
lumbar, and pelvic. The cervical curve 
commences at the apex of the odontoid 
process, and terminates at the middle of 
the second thoracic vertebra; it is convex 
in front, and is the least marked of all 
the curves. The thoracic curve, which is 
concave forward, commences at the middle 
of the second, and terminates at the middle 
of the twelfth thoracic vertebra. Its most 
prominent point behind corresponds to the 
spine of the seventh thoracic vertebra. The 
lumbar curve commences at the middle of 
the last thoracic vertebra, and terminates 
at the sacrovertebral angle. It is convex 
anteriorly; the convexity of the lower three 
vertebrae being much greater than that of 
the upper two. The pelvic curve com- 
mences at the sacrovertebral articulation 
and terminates at the point of the coccj^x. 
It is concave anteriorly. The thoracic and 
pelvic curves are the primary curves, and 
begin- to be formed at an early period of 
fetal life, and are due to the shape of the 
bodies of the vertebrae. The cervical and 
lumbar curves are compensatory or sec- 
ondary, and are developed after birth in 
order to maintain the erect position. They 
are due mainly to the shape of the in- 
tervertebral disks. Not uncommonly the 
thoracic portion of the vertebral column — 
even in healthy persons — deviates toward 
the right. This is due to the position of 
the heart and of the arch of the aorta. 

The movable part of the vertebral column 
presents for examination an anterior, a pos- 
terior, and two lateral surfaces; a base, a 
summit, and the vertebral canal. 



THE VERTEBBAL COLUMN AS A WHOLE 67 

Surfaces. — The anterior or ventral surface presents the bodies of the vertebra; 
separated in the recent state by the intervertebral disks. The bodies are broad 
in the cervical region, narrow in the upper part of the thoracic, and broadest in 
the himbar region. The whole of this surface is convex transversely, concave 
from above downward in the thoracic region, and convex in the same direction 
in the cervical and lumbar regions. 

The posterior or dorsal surface presents in the median line the spinous pro- 
cesses. These are short, horizontal, with bifid extremities, in the cervical region. 
In the thoracic region they are directed obliquely above, assume almost a vertical 
direction in the middle, and are horizontal below, as are also the spines of the 
lumbar vertebrae. They are separated by considerable intervals in the loins, 
by narrower intervals in the neck, and are closely approximated in the middle 
of the thoracic region. On either side of the spinous processes, extending the 
whole length of the column, is the vertebral groove formed by the laminse in the 
cervical and lumbar regions, where it is shallow, and by the laminae and transverse 
processes in the thoracic region, where it is deep and broad. In the recent state 
these grooves lodge the deep muscles of the back. External to each vertebral 
groove are the articular processes, and still more externally are the transverse 
processes. In the thoracic region the latter processes stand backward, on a plane 
considerably posterior to that of like processes in the cervical and lumbar regions. 
In the cervical region the transverse processes are placed in front of the articular 
processes, and on the outer side of the pedicles, between the intervertebral 
foramina. In the thoracic region they are posterior to the pedicles, inter- 
vertebral foramina, and articular processes. In the lumbar region they are placed 
in front of the articular processes, but behind the intervertebral foramina. 

The lateral surfaces are separated from the dorsal surface by the articular 
processes in the cervical and lumbar regions, and by the transverse processes 
in the thoracic region. These surfaces present in front the sides of the bodies of 
the vertebrse, marked in the thoracic region by the facets for articulation with 
the heads of the ribs. More posteriorly are the intervertebral foramina, formed 
by the juxtaposition of the intervertebral notches, oval in shape, smallest in the 
cervical and upper part of the thoracic regions, and gradually increasing in size to 
the' last lumbar vertebra. They are situated between the transverse processes in the 
neck, and in front of them in the back and loins, and transmit the spinal nerves. 

Base. — The base of that portion of the vertebral column formed by the 
twenty-four movable vertebrae is formed by the under surface of the body of the 
fifth lumbar vertebra; and the summit by the upper surface of the atlas. 

Vertebral Canal. — ^The vertebral canal follows the different curves of the verte- 
bral column; it is largest in those regions in which the vertebral column enjoys 
the greatest freedom of movement, as in the neck and loins, where it is wide and 
triangular; and is narrow and cylindrical in the back, where motion is more limited. 

Surface Form.— The only parts of the vertebral column -svhich lie closely under the skin, and 
so directly influence surface form, are the apices of the spinous processes. These are always 
distinguishable at the bottom of a median furrow, which, more or less evident, runs down the 
mesal line of the back from the external occipital protuberance above to the middle of the sacrum 
below. Occasionally one of these processes deviates a little from the median line — a fact to be 
remembered in practice, as irregularities of this kind are attendant also on fracture or displace- 
ments of the vertebral column. In the cervical region the furrow is between the Trapezii 
muscles; in the back and loins it is between the Erector spinae muscles. In the neck the furrow 
is broad, and terminates in a conspicuous projection, which is caused by the spinous process of 
the seventh cervical vertebra {vertebra promincns). Above this the spinous process of the sLxth 
cervical vertebra may sometimes be seen projecting; the other cervical spines are sunken, and 
are not visible, though the spine of the axis can be felt, and generally also the spines of the third, 
fourth, and fifth cervical vertebra;. In the thoracic region the furrow is shallow, and durmg 
stooping disappears, and then the spinous processes become more or less visible. The markmgs 
produced by these spines are small and close together. In the lumbar region the fm-row is 
deep, and the situation of the lumbar spines is frequently indicated by little pits, or depressions, 



68 SPECIAL ANATOMY OF THE SKELETON 

especially if the muscles in the loins are well developed and the process incurved. They are much 
larger and farther apart than in the thoracic region. In the sacral region the furrow is shallower, 
presenting a flattened area which terminates below at the most prominent part of the posterior 
surface of the sacrum, formed by the spinous processes of the third sacral vertebra. At the bottom 
of the furrow may be felt the irregular posterior surface of the bone. Below this, in the deep 
groove leading to the anus, the coccyx may be felt. The only other portions of the vertebral 
column which can be felt from the surface are the transverse processes of three of the cervical 
vertebrae, viz., the first, the sLxth, and the seventh. The transverse process of the atlas can be 
felt as a rounded nodule of bone just below and in front of the apex of the mastoid process, 
along the anterior border of the Sternomastoid. The transverse process of the sixth cervical 
vertebra is of surgical importance. If deep pressure be made in the neck in the course of the 
carotid artery, opposite the cricoid cartilage, the prominent anterior tubercle of the transverse 
process of the sixth cervical vertebra can be felt. This has been named Chassaignac's tubercle, 
and against it the carotid artery may be most conveniently compressed by the finger. The 
transverse process of the seventh cervical vertebra can also often be felt. Occasionally the ante- 
rior root, or costal process, is large and separate, forming a cervical rib. 

Applied Anatomy. — It is frequently necessary to locate certain vertebr». Several of them 
can be easily found and identified. The seventh cervical spine is conspicuously prominent, and 
when the skin over it has been marked with a blue pencil the spine of the sixth cervical above and 
of the first thoracic below may be located. The spine of the third thoracic vertebra is on a level 
with the root of the spine of the scapula. The spine of the fourth lumbar vertebra is on a level 
with the highest point of the iliac crest. When one or two vertebrae have been definitely recog- 
nized the other ones can be found by counting the spines from a fixed point or from fixed points. 
Over the fifth lumbar spine there is no prominence, but a depression. The third sacral spine 
is on a level with the posterior superior spines of the ilium. The level at which the spinal cord 
terminates should be known to the surgeon if he proposes to tap the spinal theca {lumbar punc- 
ture) for diagnostic or therapeutic purposes or for spinal anesthesia. In an adult the cord terminates 
at the lower border of the first lumbar vertebra, and the theca terminates opposite the body of the 
third sacral vertebra. In a young child the cord terminates opposite the body of the third lumbar 
vertebra, and the theca ends at about the same level as in an adult. Hence, in either a child 
or an adult, a puncture below the level of the fourth lumbar vertebra will infiict no injury upon 
the cord. In children the puncture is made just beneath the spinous process, and in adults 
about one-half an inch to either side of the spinous process, although the needle should be made 
to enter the dura in the median line. In either case the needle is directed upward and forward. 
As previously pointed out, the surgical anatomy of an infant's spine is not identical with the sur- 
gical anatomy of an adult's spine. The umbilicus of an infant is opposite the body of the fourth 
lumbar vertebra; in an adult it is opposite the spinous process of the third lumbar vertebra. 
In an infant the base of the sternum is on a level with the top of the seventh cervical spine, and 
in an adult of the second thoracic spine (A. H. Tubby). The vertebral column may be the seat 
of tuberculosis, which may destroy the bodies of the vertebrae; in such cases a deflection of the 
column may be directed either forward or backward. This deflection is produced by the great 
weight of the trunk on the diseased bone. If the deflection is directed forward, it is called 
lordosis; if backward, kyphosis. Scoliosis (lateral deviation of the vertebral column) is usually 
due to a faulty attitude of children while standing or while sitting at school desks. 

Occasionally the coalescence of the laminfe is not completed, and consequently a cleft is left 
in the arches of the vertebrae, through which a protrusion of the spinal membranes (dura mater 
and arachnoid), and sometimes of the spinal cord itself, takes place, constituting a malformation 
known as spina bifida or hydrorhacliitis. This condition is most common in the lumbosacral 
region ; but it. may occur in the thoracic or cervical region, or the arches throughout the whole 
length of the canal may remain unapproximated. In some rare cases, in consequence of the 
noncoalescence of the two primary centres from which the body is formed, a similar condition 
may occur in front of the canal, the bodies of the vertebrae being found cleft and the tumor 
projecting into the thorax, abdomen, or pelvis, between the lateral halves of the bodies aft'ected. 

The construction of the spinal column of a number of pieces, securely connected together 
and enjoying only a slight degree of movement between any two individuals pieces, though 
permitting of a very considerable range of movement, as a whole, allows a sufficient degree of 
mobility without any material diminution of strength. The main joints of which the spine is 
composed, together with the very varied movements to which it is subjected, render it liable to 
sprains, which may complicate other injuries or may exist alone; but so closely are the individual 
vertebrae articulated that these sprains are seldom severe, and an amount of violence sufficiently 
great to produce tearing of the ligaments would tend to cause a dislocation or fracture. The 
further safety of the column and its less liability to injury is provided for by its disposition in 
curves instead of in one straight line. For it is an elastic column, and must first bend before 
it breaks; under these circumstances, being made up of three curves, it represents three columns, 
and greater force is required to produce bending of a short column than of a longer one that is 
equal to it in breadth and material. Again, the safety of the column is provided for by the inter- 
position of the intervertebral disks between the bodies of the vertebrae, which act as admirable 



THE SKULL 



69 



buffers in counteracting the effects of violent jars or shocks. Fracture didncation of the verteliral 
column may be caused by direct or indirect violence, or by a combination of the two, as when 
a person falling from a height strikes against some prominence and is doubled over it. The 
fractures from indirect violence are the more common, and here the bodies of the vertebrte are 
compressed, while the arches are torn asunder; while in fractures from direct violence the arches 
are compressed and the bodies of the vertebrae separated from each other. It will therefore be 
seen that in both classes of injury the spinal cord is the part least likely to be injured, and may 
escape damage even when there has been considerable lesion of the bony framework. For, as 
Mr. Jacobson states, "being lodged in the centre of the column, it occupies neutral ground in 
•respect to forces which might cause fracture. For it is a law in mechanics that' when a beam, 
as of timber, is exposed to breakage and the force does not exceed the limits of the strength of 
the material, one division resists compression, another laceration of the particles, while the third, 
between the two, is in a negative condition."' Applying this principle to the vertebral column, 
it will be seen that, whether the fracture dislocation be produced by direct violence or by indirect 
force, one segment, either the anterior or posterior, will be exposed to compression, the other to 
laceration, and the intermediate part, where the cord is situated, will be in a neutral state. When 
a fracture dislocation is produced by indirect violence the displacement is almost always the same, 
the upper segment being driven forward on the lower, so that the cord is compressed between the 
body of the .vertebra below' and the arch of the vertebra above. 

The parts of the vertebral column most liable to be injured are (1) the thoracolumbar region, 
for this part is near the middle of the column, and there is therefore a greater amount of leverage, 
and, moreover, the portion above is comparatively fixed, and the vertebrae which form it, though 
much smaller, have nevertheless to bear almost as great a weight as those below; (2) the cervico- 
thoracic region, because here the flexible cervical portion of the vertebral column joins the more 
fixed thoracic region; and (3) the atlantoaxial region, because it enjoys an extensive range of 
movement, and, being near the skull, is influenced by violence applied to the head. In fracture 
dislocation, spinous processes and portions of the laminae may be removed {laminectomy) in order 
to free the spinal cord from pressure, and to permit the surgeon to explore, to arrest hemorrhage, 
to remove bone fragments, or to apply sutures. Laminectomy is also resorted to in some cases 
of paraplegia due to Pott's disease of the spine. 

THE SKULL. 

The Skull, or superior expansion of the vertebral cohimn, has been described 
as if composed of four vertebrae, the elementary parts of which are specially 
modified in form and size, and almost immovably connected, for the reception 
of the brain and special organs of the senses. These vertebrae are the occipital 
parietal, frontal, and nasal. Descriptive anatomists, however, divide the skull 
into two parts, the Cranium and the Face. The Cranium is composed of eight 
bones, viz., the occipital, two parietals, frontal, two temporals, sphenoid, and ethmoid. 
The Face is composed of fourteen bones, viz., the two nasals, two maxillce, two 
lacrimals, two malars, two palates, two turbinates, vomer, and mandible. The ossic- 
uli auditus, the teeth, and Wormian hones are not included in this enumeration. 

Occipital. 



Skull, 22 bones 



Two parietals. 
Cranium, 8 bones . ^ Twftemporals. 



Sphenoid. 
L Ethmoid. 
f Two nasals. 

Two maxillae. 

Two lacrimals. 

r, , . J I Two malars. 

Face, 14 bones . . < ^^^,^ ^.^^^^^^ 

Two turbinates. 
I Vomer. 
L Mandible. 

The Hyoid Bone, situated at the root of the tongue and attached to the base 
of the skull by ligaments, has also to be considered in this section. 

' Holmes' System of Surgery, 1883, vol. i, p. 529. 



70 



SPECIAL ANATOMY OF THE SKELETON 



THE CEREBRAL CRANIUM (CRANIUM CEREBRALE) 
The Occipital Bone (Os Occipitale). 

The occipital bone is situated at the back part and base of the cranium, is curved 
on itself, and is trapezoidal in shape. The bone presents for examination two 
surfaces, four borders, and four angles. 

Surfaces. — The external surface is convex. Midway between the summit 
of the bone and the posterior margin of the foramen magnum — a large oval 
opening for transmission of the spinal cord — is a prominent tubercle, the external 
occipital protuberance { protuberantia occipitalis externa), and, descending from it 



Lmea 
sup) 




as far as the foramen, a vertical ridge, the external occipital crest (crista occipitalis 
externa). This protuberance and crest give attachment to the ligamentum nuchae 
and Trapezius, and vary in prominence in different skulls. Passing outward from 
the occipital protuberance is a semicircular ridge on each side, the superior curved 
line (linea niiclme superior). Above this line there is often a second less distinctly 
marked ridge, called the highest curved line (linea nuchae suprema); to it tlie 
epicranial aponeurosis is attached. The bone between these two lines is smoother 
and denser than the rest of the surface. Running parallel with these from the 
middle of the crest is another semicircular ridge, on each side, the inferior curved 
line (linea nuchae inferior). The surface of the bone above the linea suprema is 
rough and porous, and in the recent state is covered by the Occipitofrontalis 
muscle. The superior and inferior curved lines, together with the surfaces of 
bone between and below them, serve for the attachment of several muscles. 



THE OCCIPITAL BONE 



71 



The superior curved line gives attachment internally to the Trapezius, externally 
to the muscular origin of the Occipitofrontalis, and to the Sternomastoid to the 
extent shown in Fig. 39; the depressions between the curved lines to the Com- 
plexus internally, the Splenius capitis and Obliquus capitis superior externally. 
The inferior curved line and the depressions below it afford insertion to the Rectus 
capitis posticus, major and minor. 

The foramen magnum {foramen occipitale magnum) is a large, oval apertiu'e, 
its long diameter extending from before backward. It transmits the lower por- 
tion of the medulla oblongata and its membranes, the spinal part of the spinal 
accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries, 
and the occipitoaxial ligaments. Its back part is wide for the transmission of 
the medulla oblongata, and the corresponding margin rough for the attachment 
of the dura enclosing it; the fore part is narrower, being encroached upon by the 
condyles; it has projecting toward it, from below, the odontoid process, and its 
margins are smooth and bevelled internally to support the meclulla oblongata. 
On each side of the foramen magnum are the condyles for articulation with the 
atlas. Each condyle (condylus occipitalis) is convex, oval, or reniform in shape, 
and directed downward and outward. The condyles converge in front, and 
encroach slightly upon the anterior segment of the foramen. On the inner border 
of each condyle is a rough tubercle for the attachment of the ligaments (check) 
which connect this bone with the odontoid process of the axis; while external to 
tliem is a rough tubercular prominence, the transverse or jugular process (processus 
jugularis), channelled in front by a deep notch (incisura jugularis), which forms, 
part of the jugular foramen (foramen lacerum posterius). The under surface of 
this process presents an eminence (processus intrajugularis) , which represents the 
paramastoid process of some mammals. The eminence is occasionally large, and 
extends as low as the transverse process of the atlas. This surface affords attach- 
ment to the Rectus capitis lateralis muscle and to the lateral occipitoatlantal 
ligament; its upper or cerebral surface presents a deep groove, which lodges part 
of the lateral sinus, while its external surface is marked by a quadrilateral rough 
facet, covered with cartilage in the fresh state, and articulating with a similar 
surface on the petrous portion of the temporal bone. On the outer side of each 
condyle, near its fore part, is a foramen, the anterior condylar foramen (canalis 
hypoglossi); it is directed downward, outward, and forward, and transmits the 
hypoglossal nerve, and occasionally a meningeal branch of the ascending pharyn- 
geal artery. This foramen is sometimes double. Behind each condyle is a 
fossa^ (fossa condyloideus), sometimes perforated at the bottom by a foramen, 
the posterior condylar foramen (canalis condyloideus), for the transmission of a 
vein to the lateral sinus. The basilar process (pars basilaris) is a strong quadri- 
lateral plate of bone, which is wider behind than in front, and is situated in front 
of the foramen magnum. Its under surface is rough, presents in the median line 
a tubercular ridge, the pharyngeal spine {tuherculuni pharyngeum), for the attach- 
ment of the tendinous raph^and Superior constrictor of the pharynx, and on each 
side of it rough depressions for the attachment of the Rectus capitis anticus, 
major and minor. 

The internal surface (Fig. 40) is deeply concave. The posterior part is divided 
by a crucial ridge into four fossa?. The two superior fossa; receive the occipital 
lobes of the cerebrum, and present slight eminences and depressions corresponding 
to their convolutions. The two inferior, which receive the hemispheres of the 
cerebellum, are larger than the former, and comparatively smooth ; both are marked 
by slight grooves for the lodgement of arteries. At the point of meeting of the four 

> This fossa presents many variations in size. It is usually shallow, and the foramen small; occasionally 
wanting on one or both sides. Sometimes both fossa and foramen are large, but confined to one side only; more 
rarely, the fossa and foramenare very large on both sides. 



72 



SPECIAL ANATOMY OF THE SKELETON 



divisions of the crucial ridge is an eminence, the intemal occipital protuberance {yro- 
tuberantia occipitalis interna). It nearly corresponds to that on the outer surface, 
though it is often on a slightly higher level, and is perforated by one or more 
large vascular foramina. From this eminence the superior division of the crucial 
ridge runs upward to the superior angle of the bone; it presents a deep groove, 
.the sagittal sulcus (sulcus sagittalis), for the superior saggittal sinus. The 
margins of the groove give attachment to the falx cerebri. The inferior division, 
the intemal occipital crest (crista occipitalis interna), runs to the posterior margin 
of the foramen magnum, on the edge of which it becomes gradually lost; this 



Superior 




Inferior angle. 
Fig. 40, — Occipital bone. Inner surface. 

ridge, which is bifurcated below, serves for the attachment of the falx cerebelli. 
It is usually marked by a single groove, which commences at the back part of 
the foramen magnum and lodges the occipital sinus. Occasionally the groove 
is double where two sinuses exist. A transverse groove (sulcus transversus) passes 
outward on each side to the lateral angle. The grooves are deep channels for 
the lodgement of the lateral sinuses, their prominent margins affording attachment 
to the tentorium.^ At the point of meeting of these grooves is a depression, 
the torcular^ (confluens sinuum), placed a little to one or the other side of the internal 

1 Usually one of the transverse grooves is deeper and broader than the other; occasionally, both grooves are 
of equal depth and breadth, or both equally indistinct. The broader of the two transverse grooves is nearly 

•always continuous with the vertical groove for the superior sagittal sinus, 

2 The columns of blood coming in different directions were supposed to be pressed together at this point 
iiorcular, a wine press). 



THE OCCIPITAL BONE 73 

occipital protuberance. More anteriorly is the foramen magnum, and on each 
side of it, but nearer its anterior than its posterior part, the internal openinn's 
of the anterior condylar foramen. On the superior aspect of the lateral portion 
of the bone the jugular tubercle (tuherculum jugulare) is seen. This corresponds 
to the portion of bone which roofs in the anterior condylar foramen. The 
internal openings of the posterior condylar foramina are a little external and 
posterio ■ to the openings of the anterior condylar foramina, protected by a small 
arch of bone. At this part of the internal surface there is a very deep groove in 
which the posterior condylar foramen, when it exists, has its termination. This 
groove is continuous, in the complete skull, with the transverse groove on the 
posterior part of the bone, and lodges the end of the lateral sinus. In front 
of the foramen magnum is the basilar process, presenting a shallow depression, 
the basilar groove (clivus), which slopes from behind, upward and forward, and 
supports the medulla oblongata and part of the pons (Varolii), and on each side 
of the basilar process is a narrow channel, which, when united with a similar 
channel on the petrous portion of the temporal bone, forms a groove (sulcus 
peiros'us inferior), which lodges the inferior petrosal sinus. 

Borders. — The superior border (viargo lambdoideus). extends on each side 
from the superior to the lateral angle, is deeply serrated for articulation with the 
parietal bone, and forms, by this union, the lambdoid suture. 

The inferior border extends from the lateral to the inferior angle; its upper half 
(marcjo mastoideus) is rough, and articulates with the mastoid portion of the tem- 
poral, forming the masto-occipital suture; the inferior half articulates with the 
petrous portion of the temporal, forming the petro-occipital suture ; these two por- 
tions are separated from each other by the jugular process. In front of this 
process is a deep notch, which with a similar one on the petrous portion of the 
temporal forms the jugular foramen (foramen, lacerum posterius). This notch 
is occasionally subdivided into two parts by a small process of bone (processus 
intrajugularis) , and it generally presents an aperture at its upper part, the internal 
opening of the posterior condylar foramen. 

Angles.. — The superior angle is received into the interval between the posterior 
superior angles of the two parietal bones; it corresponds with that part of the 
skull in the fetus which is called the posterior fontanelle. 

The inferior angle is represented by the square-shaped surface of the basilar 
process. At an early period of life a layer of cartilage separates this part of 
the bone from the sphenoid, but in the adult the union between them is osseous. 

The lateral angles correspond to the outer ends of the transverse grooves, and 
are received into the interval between the posterior inferior angles of the parietal 
and the mastoid portion of the temporal. 

Structure. — The occipital bone consists 
of two compact laminse, called the outer 
and inner tables, having between them 
the diploic tissue; this bone is especially 
thick at the ridges, protuberances, con- 
dyles, and anterior part of the basilar 
process; while at the bottom of the fossae, 
especially the inferior, it is thin, semitrans- 
parent, and destitute of diploe. 

Development (Fig. 41).— At birth the 
bone consists of four distinct parts — a 
tabular or squamous portion, which \&f^ -1 for basilar portion. ,. 

lies behind the foramen magnum; two ^ ,, x, , ^^"^ j. r ■ •» i v, -r =o„o„ 

, ,. , ■ I P P ■ , ,. Fig. 41. — Development of occipital bone. From seven 

condylic parts, which form the sides 01 centres, 

the foramen; and a basilar part, which 

lies in front of the foramen. The tabular portion is usually developed from four centres, though 
the number may vary from one to eight; two centres appear near the median line of the bone 




74 SPECIAL ANA TOMY OF THE SKELETON 

during the second month, and two more a little lateral to the preceding during the third month. 
These parts tend to unite, but complete union does not occur until about the fourth month after 
birth. That part of the tabular portion above the highest curved line is developed by the 
iidramembranous method, and may exist in the adult as a separate element, the interparietal 
bone, or os incae, because of its frequent occurrence in Peruvian skulls. The remainder of 
the tabular portion and the basilar and two condyloid parts are developed from cartilage. 
Usually two centres appear in the basilar portion during the sixth fetal week, and by rapid 
coalescence give the appearance of a single centre. Each condylic portion develops from a 
single centre that appears at about the end of the eighth fetal week. At about the fourth 
year the tabular and the two condyloid pieces unite, and about the sixth year the bone 
consists of a single piece. Between the eighteenth and twenty-fifth years the occipital and 
sphenoid become united, forming a single bone. 

Articulations. — With six bones — two parietal, two temporal, sphenoid, and atks. 

Attachment of Muscles. — To twelve pairs — to the superior curved line are attached the 
Occipitofrontalis, Trapezius, and Sternomastoid. To the space between the curved lines, the 
Complexus,^ Splenius capitis, and Obliquus capitis superior; to the inferior curved line, and 
the space between it and the foramen magnum, the Rectus capitis posticus, major and minor; 
to the transverse process, the Rectus capitis lateralis; and to the basilar process, the Rectus 
capitis anticus, major and minor, and Superior constrictor of the pharynx. 



The Parietal Bone (Os Parietale). 

The parietal bones are paired bones, and form, by their union, the sides and 
roof of the cranium proper. Each bone is of an irregular quadrilateral form, 
and presents for examination two surfaces, four borders, and four angles. 

Surfaces. — The external surface (fades parietalis) (Fig. 42) is convex, smooth, and 
marked about its centre by an eminence called the parietal eminence {tuber parietale), 
which indicates the point where ossification commenced. Crossing the middle 
of the bone in an antero-posterior direction are two well-marked curved ridges, 
the upper and lower temporal ridges (linea temporalis superior et inferior-) ; the former 
gives attachment to the temporal fascia, while the latter indicates the upper limit 
of the origin of the Temporal muscle. These lines form the temporal crest. 
Above these ridges the surface of the bone is covered by the aponeurosis of the 
Occipitofrontalis; below them the bone forms part of the temporal fossa, and 
affords attachment to the temporal muscle. At the back part, of the superior 
border, close to the sagittal suture, which separates the two parietal bones, is a 
small foramen (foramen parietale), which transmits the emissary vein of Santorini 
to the scalp from the superior sagittal sinus. It sometimes also transmits a 
small branch of the occipital artery. Its existence is not constant, and its size 
varies considerably. 

The internal or cerebral surface (fades cerebralis') (Fig. 43) is concave, presents 
depressions for the lodgement of the convolutions of the cerebrum, and numerous 
furrows for the branches of the middle meningeal artery; the latter runs upward 
and backward from the anterior inferior angle and from the central and posterior 
part of the lower border of the bone. Sometimes a distinct canal exists for the 
artery, but it never remains a canal for a long distance. Along the upper .margin 
of the bone is part of a shallow groove, which, when joined to the opposite parietal, 
forms a channel for the superior sagittal sinus. The elevated edges of the groove 
afford attachment to the falx cerebri. Near the groove are seen several depres- 
sions. Pacchionian depressions (foveolae granulares [Pacchioni]). They are most 
frequently foimd in the skulls of old persons, and lodge the arachnoid villi (Pacchi- 
onian bodies). The interna! opening of the parietal foramen is also seen when 
that aperture exists. On the inner surface of the posterior inferior portion of 
the bone is a portion of the groove for the lodgement of the lateral sinus. 

* To these the Biventer cervicis should be added, if it is regarded as a separate muscle. 



THE PARIETAL BONE 



75 




occipital bone. 



of te-Ki-V 
Fig. 42. — Left parietal bone. External surface. 




Fig. 43. — Left parietal bone. Internal surface. 



76 SPECIAL ANATOMY OF THE SKELETON 

Borders. — The superior border (margo sagiUalis), the longest and thickest, 
is dentated to articulate with its fellow of the opposite side, forming the sagittal 
suture. 

The inferior border (niargo squamosus) is divided into three parts; of these, 
the anterior is thin and pointed, bevelled at the expense of the outer surface, and 
overlapped by the tip of the greater wing of the sphenoid; the middle portion is 
arched, bevelled at the expense of the outer surface, and overlapped by the 
squamous portion of the temporal; the posterior portion is thick and serrated for 
articulation with the mastoid portion of the temporal. 

The anterior border [margo frontalis), deeply serrated, is bevelled at the expense 
of the outer surface above and of the inner below; it articulates with the frontal 
bone, forming the coronal suture. 

The posterior border (margo occipitalis), deeply denticulated, articulates with 
the occipital, forming the lambdoid suture. 

Angles. — The anterior superior angle (angulus frontalis), thin and pointed, 
corresponds with that portion of the skull which in the fetus is membranous, and 
is called the anterior fontanelle {bregma). 

The anterior inferior angle (angulus sphenoidalis) is thin and lengthened, being 
received in the interval between the greater wing of the sphenoid and the frontal. 
Its inner surface is marked by a deep groove, sometimes a canal, for the anterior 
branch of the middle meningeal artery. At the anterior inferior angle the parietal 
and frontal bones and the greater wing of the sphenoid bone meet. This spot is 
called the pterion. 

The posterior superior angle (angulus occipitalis) corresponds with the junction 
of the sagittal and lambdoid sutures. In the fetus this part of the skull is mem- 
branous, and is called the posterior fontanelle (lambda). 

The posterior inferior angle (angulus mastoideus) articulates with the mastoid 
portion of the temporal bone, and generally presents on its inner surface a broad, 
shallow groove for the lodgement of part of the lateral sinus. 

Development. — The parietal bone is formed in membrane, being developed from one centre, 
which corresponds with the parietal eminence, and makes its first appearance about the seventh 
or eighth week of fetal life. Ossification gradually extends from the centre to the circumference 
of the bone; the angles are consequently the parts last formed, and it is in their situation that the 
fontanelles exist previous to the completion of the growth of the bone. Occasionally the parietal 
bone is divided into two parts, upper and lower, by an antero-posterior suture. 

Articulations. — With five bones — the opposite parietal, the occipital, frontal, temporal, and 
sphenoid. 

Attachment of Muscles.— 0»e only, the Temporal. ^ 



The Frontal Bone (Os Frontale). 

The frontal bone consists of two portions — a vertical or frontal portion, situated 
at the anterior part of the cranium proper, forming the forehead; and a horizontal 
or orbital portion, which enters into the formation of the roof of the orbits and 
nasal fossae. 

Vertical Portion. Surfaces. — External Surface (fades frontalis) (Fig. 44). — In 
the median line, traversing the bone from the upper to the lower part, is occasionally 
seen a slightly elevated ridge, and in young subjects a suture (frontal or metopic 
suture) which represents the line of union of the two lateral halves of which the bone 
consists at an early period of life; in the adult this suture is usually obliterated and 
the bone forms one piece. On either side of this ridge, a little below the centre of 
the bone, is a rounded prominence, the frontal eminence (tuber frontale). These 
eminences vary in size in different individuals, and are occasionally unsymmetrica! 



THE FRONTAL BONE 



77 



in the same subject. The whole surface of the bone above this part is sinootli, 
and covered by the aponeurosis of the Occipitofrontalis muscle. Below the frontal 
eminence and separated from it by a slight groove is the superciliary ridge (arcus 
super ciliar is), broad internally, where it is continuous with the nasal eminence, 
but less distinct as it arches outward. These ridges are caused by the projection 
outward of the frontal air sinuses/ and give attachment to the Orbicularis 
palpebrarum and Corrugator supercilii. Between the two superciliary ridges 
is a smooth, flat surface, the glabella. Beneath the superciliary ridge is the 
supraorbital arch (margo supraorbitalis), a curved and prominent margin, which 
forms the upper boundary of the orbit and separates the vertical fi-om the hori- 
zontal portion of the bone. The outer part of the arch is sharp and prominent, 
affording to the eye, in that sititation, considerable protection from injury; 




the inner part is less prominent. At the junction of the internal and middle 
third of this arch is a notch, sometimes converted into a foramen, and called the 
supraorbital notch {incistira supraorbitalis). It transmits the supraorbital artery, 
vein, and nerve. A small aperture is seen in the upper part of the notch, which 
transmits a vein from the diploe to join the supraorbital vein. To the median 
side of the supraorbital notch there is often a notch (incisura frontalis) for the 
passage of the frontal artery and nerve. The supraorbital arch terminates 
externally in the external angular process and internally in the internal angular 



1 Some confusion is occasioned to students commencing the study of anatomy by the name ' 'sinuses ha\ing 
bsen given to two perfectly different kinds of spaces connected with the sliull. It miiy be .is well, therefore, to 
state here, at the outset, that the "sinuses" in tne interior of the cranium which produce the grooves on the in"cr 
surface of the bones are venous channels along which the blood runs in its passage back from the brain, while 
the "sinuses" external to the cranial cavity (the frontal sphenoidal, ethmoidal, and maxillary) are hollow 
spaces in the bones themselves which communicate with the nostrils, and contaiil air. 



78 



SPECIAL ANATOMY OF THE SKELETON 



process. The external angular process is strong, prominent, and articulates 
with the malar bone; running upward and backward from it are two well-marked 
lines, which, starting together from the external angular process as the temporal 
crest, soon diverge from each other and run in a curved direction across the ])one. 
These are the upper and lower temporal ridges ; the upper gives attachment to the 
temporal fascia, the lower to the Temporal muscle. Beneath them is a slight 
concavity that forms the anterior part of the temporal fossa and gives origin to 
the Temporal muscle. The internal angular process is less marked than the 
external, articulates with the lacrimal bones, and gives attachment to the 
Orbicularis palpebrarum. 




With maxilla 

With nasal ii , , ^ j- 7 

I ! nthi sm face of nasal pi ocess, 

With perpendicular plate of ethmoid ' foiming pait of loof of nose 
Fig. 45. — Frontal "bone. Inner surface. 



Internal Surface (cerebral surface, fades cerehralis) (Fig. 45). — Along the median 
line is a vertical groove, the sulcus sagittalis, the edges of which unite below to 
form a ridge, the frontal crest {crista frontalis'); the groove lodges the superior 
sagittal sinus, while its margins afford attachment to the falx cerebri. The 
crest terminates below at a small notch which is converted into a foramen by 
articulation with the ethmoid. It is called the foramen cecum, and varies in 
size in different subjects; it is sometimes partially or completely impervious, 
lodges a process of the falx, and when open transmits a vein from the mucous 
membrane of the nose to the superior sagittal sinus. On either side of the groove 
the bone is deeply concave, presenting depressions for the convolutions of the 
brain, and numerous small furrows for the ramifications of the anterior branches 
of the middle meningeal arteries. Several small, irregular fossse are seen also on 
either side of the groove, for the reception of the arachnoid villi. 

The border of the vertical portion is thick, deepl}' serrated, bevelled at the 



THE FRONTAL BONE 



79 



expense of the internal table above, where it rests upon the parietal iKjnes, and 
at the expense of the external table at each side, where it receives the lateral 
pressure of those bones; this border is continued below into a triangular rough 
surface which articulates with the greater wing of the sphenoid. 

Horizontal or Orbital Portion. — ^This portion of the bone consists of two thin 
plates, the orbital plates, wiiich form the vault of the orbit, separated from one 
another by a median gap, the ethmoidal notch. 

Surfaces. Orbital Surface. — The surface of each orbital plate {fades orhitali.s) 
consists of a smooth, concave, triangular lamina of bone, marked at its front 
and external part ( immediately beneath the external angular process) by a shallow 
depression, the lacrimal fossa {fossa cilandulae lacrimalis), occupied by the lacrimal 
gland; and at its anterior and internal part by a depression (sometimes a small 
tubercle), the trochlear fossa {fovea trochlearis), for the attachment of the carti- 
laginous pulley of the Superior oblique muscle of the eye. These plates are united 
in front by a roughened uneven surface called the nasal process, which articulates 
in front with the nasal bones, laterally with the nasal process of each maxilla. 
From the middle of the nasal process a thin lamina of bone (the nasal spine) 
projects downward and forward; on either side of this is a shallow groove, which 
enters into the formation of the nasal fossa. The nasal spine articulates in front 
with the nasal bones and behind with the perpendicular plate of the ethmoid, 
and by so doing assists in forming the septum of the nose. The ethmoidal notch 
(incisura ethvioidalis) separates the two orbital plates; it is quadrilateral, and 
occupied, when the bones are united, by the cribriform plate of the ethmoid. 
The margins of this notch present several half cells, which, when united with 
corresponding half cells on the upper surface of the ethmoid, complete the eth- 
moidal cells; two grooves are also seen crossing these edges obliquely; they are 
con\erted into canals by articulation with the ethmoid, and are called the anterior 
and posterior ethmoidal canals {foramen ethmoidale anterius and foramen ethvioidale 
posterius) ; they open on the inner wall of the orbit. The anterior one transmits 
the nasal nerve and anterior ethmoidal vessels; the posterior one, the posterior 
ethmoidal vessels. In front of the ethmoidal notch, on each side of the nasal 
process, is the opening of the frontal air sinus {sinus frontalis). These are two 
irregular cavities, which extend upward and outward, a variable distance, between 
the two tables of the skull, and are separated from each other by a thin bony 
septum {septum simnim frontalium) , which is often displaced to one side. Within 
the sinuses imperfect trabecule of bone often exist. The sinuses are beneath 
and gi\e rise to the prominences above the supraorbital arches called the super- 
ciliary ridges {arciis snperciliares). The frontal air sinuses are absent at birth, 
become apparent about the seventh year of life, and from this period until the 
age of twenty gradually increase in size. Sometimes, however, the sinuses remain 
very small or never develop at all — or one side may be large and the other small — 
or one may exist on one side and be absent on the other. The right sinus is usually 
the larger. These cavities are larger in men than in women. The floor of each 
sinus is very thin and is over the orbit and the upper border of the lateral mass 
■of the ethmoid. The thinnest portion of the floor is at the upper and inner 
angle of the orbit. The frontal sinuses are lined by mucous membrane, and 
each sinus communicates with the middle meatus of the nose by the infundi- 
bulum. In some cases the sinuses communicate with each other by means of 
an aperture in the septum and occasionally join the sinus in the crista galli of 
the ethmoid. 

The internal surface {cerebral surface, fades cercbralis) of the horizontal portion 
presents the convex upper surfaces of the orbital plates, separated from each other 
in the median line by the ethmoidal notch, and marked by eminences and de- 
pressions for the convolutions of the frontal lobes of the cerebrum. 




80 SPECIAL ANATOMY OF THE SKELETON 

The border of the horizontal portion is thin, serrated, and articulates with 
the lesser wing of the sphenoid. 

Structure. — The frontal portion and external angular processes consist of diploic tissue sur- 
rounded by compact bone. In the frontal sinus region the cancellous tissue is wanting. The 
horizontal portion is thin, translucent, and composed entirely of compact tissue. 

Development (Fig. 46). — The frontal bone is 
formed in membrane, being developed from two 
primary centres, one for each lateral half, which 
make their appearance about the seventh or 
eighth week, above the orbital arches. From 
this point ossification extends, in a radiating 
manner, upward into the forehead and backward 
over the orbit. The nasal spine is developed 
from two secondary centres, while additional cen- 
tres appear in the regions of the internal and 
external angular processes. Sometimes a centre 
appears on either side at the lower end of the 
coronal suture. This latter centre sometimes re- 
mains ununited, and is known as the pterion. 
, ossicle, or it may join with the parietal, sphenoid, 

;. ° ° or temporal bone. At birth the bone consists 

of two pieces, which afterward become united, 
along the median line, by a suture (metopic) which runs from the vertex to the root of the nose. 
This suture usually becomes obliterated within a few years after birth, but it occasionally remains 
throughout life. 

Articulations. — With twelve bones — two parietal, the sphenoid, the ethmoid, two nasal, two 
maxillse, two lacrimal, and two malar. 

Attachment of Muscles. — To three pairs — the Corrugator supercilii, Orbicularis palpe- 
brarum, and Temporal, on each side. 



The Temporal Bone (Os Temporale). 

The temporal bone consists of three parts — (a) the squamous, (6) the petro- 
mastoid, and (c) the tympanic portions — which, though separate in early life, 
become united in the adult. The three parts meet and form a part of the 
outer wall and a part of the base of the skull and the external auditory meatus. 

The Squamous Portion {pars squamosa temporalis). — The squamous portion, 
the anterior and upper part of the bone, is scale-like in form, and is thin and 
translucent (Fig. 47). Its external surface is smooth, convex, and grooved at 
its back part for the deep temporal arteries; it affords attachment to the Tem- 
poral muscle and forms part of the temporal fossa. At its back part may be 
seen a curved ridge (part of the temporal ridge), which serves for the attachment 
of the temporal fascia, limits the origin of the Temporal muscle, and marks 
the boundary between the squamous and mastoid portions of the bone. Pro- 
jecting from the lower part of the squamous portion is a long, arched process 
of bone, the zygoma, or zygomatic process. This process is at first directed out- 
ward, its two surfaces looking upward and downward; it then appears as if 
twisted upon itself, and runs forward, its surfaces now looking inward and out- 
ward. The superior border of the process is long, thin, and sharp, and serves 
for the attachment of the temporal fascia. The inferior, short, thick, and arched, 
has attached to it some fibres of the Masseter muscle. Its outer surface is convex 
and subcutaneous; its inner is concave, and also affords attachment to the Masse- 
ter. The extremity, broad and deeply serrated, articulates with the malar bone. 
The zygomatic process is connected to the temporal bone by three divisions, 
called its roots — an anterior, middle, and posterior. The anterior, which is short, 
but broad and strong, is directed inward, to terminate in a rounded eminence. 



THE TEMl^ORAL BONE 



SI 



the emiiientia arti.cularis. This eminence forms the front boundary of tlie 
glenoid fossa, and in the recent state is covered with cartilage. The middle 
root (posfglenoid process) forms the posterior boundary of the mandibular portion 
of the glenoid fossa; while the posterior root, which is strongly marked, runs from 
the upper border of the zygoma, in an arched direction, upward and backward, 
forming the posterior part of the temporal ridge (s2ipramastoid crest). At the 
junction of the anterior root with the zygoma is a projection, called the tubercle, 
for the attachment of the external lateral ligament of the mandible; and between 




Groove for middle 
temporal artery 



Incisura parietalis 

/ Supramental 
\ Uwn,,lc 

^'-'^^ OCCIPITO- 



Zygomatic proc 

Lnunentta 
articulans- 
Postglenoid pi ocess 

Glenoid cavity 



Glaserian fissure 

Tympavic plate 



STYLOGLOSSU 




Occipital groove 



External auditory process 
stvlohyoi'd 

Styloid process 



Fig. 47.— Left tempoiLiI bo 



Lateral surface. 



the anterior and middle roots is an oval depression, forming part (mandibular) 
of the glenoid fossa, for the reception of the condyle of the mandible. Between 
the posterior wall of the external auditory meatus and the posterior root of the 
zygoma is the area called the suprameatal triangle (Macewen), often marked by 
a spinous process (spine of Henle). 

The internal surface of the squamous portion (Fig. 48) is concave, presents 
numerous eminences and depressions for the convolutions of the cerebrum, and 
two well-marked grooves for the branches of the middle meningeal artery. 

Borders. — The superior border is thin, bevelled at the expense of the internal 
surface, so as to overlap the lower border of the parietal bone, forming the 
squamous suture. The anterior inferior border is thick, serrated, and bevelled, 
alternately at the expense of the inner and outer surfaces, for articulation with 
the greater wing of the sphenoid. 

The Petromastoid Portion {partes petrosa ct mastoidea). — The petromastoid 
portion consists of (a) a mastoid portion, the thick conical posterior part behind 



82 



SPECIAL ANATOMY OF THE SKELETON 



the external auditory meatus, and (6) a pyramidal portion named the petrous 
portion, which contains the internal ear and forms part of the floor of the cranial 

cavity- 



^to-l bone 




ETmnentia 
arcuata. 



Foramen Tnastoidev/m I 

Aquaeductus vestihuli 

AqiULeductus cockleie 

Meatus acusticus intemus 

Fig. 48. — Left temporal bone. Inner surface. 



The Mastoid Portion {pars mastoidea). — The mastoid portion is situated at 
the posterior part of the bone (Figs. 47 and 49). 

Surfaces. Outer Surface. — ^The outer surface of the mastoid is rough, and 
gives attachment to the Occipitofrontalis and Retrahens aurem muscles. It is 
perforated by numerous foramina; one of these, of large size, situated at the 
posterior border of the bone, is termed the mastoid foramen {foramen mastoidemii) ; 
it transmits a vein from the lateral sinus and a small artery from the occipital 
to supply the dura. The position and size of this foramen are very variable. 
It is not always present; sometimes it is situated in the occipital bone or in the 
suture between the temporal and the occipital. The mastoid portion is con- 
tinued below into a conical projection, the mastoid process {processus niastoidevs), 
the size and form of which vary somewhat. This process serves for the attach- 
ment of the Sternomastoid, Splenius capitis, and the Trachelomastoid. On the 
inner side of the mastoid process is a deep groove, the digastric fossa {incisura 
mastoidea), for the attachment of the Digastric muscle; and, running parallel 
with it, but more internal, the occipital groove {sulcus a. occipitalis), which lodges 
the occipital artery {fossa mastoidea). 

Internal Surface. — The internal surface of the mastoid portion presents a deep, 
cu^^'ed groove, the sigmoid fossa, which lodges part of the lateral sinus; and into 



THE TEMPORAL BONE 



83 



it may be seen opening the mastoid foramen, which transmits an emissary vein 
from the lateral' sinus to the posterior auricular or occipital vein and a small 
artery, the mastoid branch of the occipital artery. A section of the mastoid 
process (Figs. 49 and 50) shows it to contain a number of cellular spaces, com- 
municating with one another, called the mastoid cells (cellulae mastoideae), which 
exhibit the greatest possible variety as to their size and number. At the upper 
and front part of the bone these cells are large and irregular, and contain air. 
They diminish in size toward the lower part of the bone; those situated at the 
apex of the mastoid process are quite small, representing spaces of cancellous 
bone, and usually containing marrow. Occasionally they are entirely absent, and 



Mastoid antrum 



Tegmen tympani 

Prominence of extl. semicircular canal 
Prominence of facial canal 
Fenestra ovalis 
Bristle in canal for Tensor tympani 
Processus cocldeariformis 
Bnstle in hiaivs Fallopii 




Mastoid cells 



Carotid canal 
Bony pa} t of Eustachian tube 
Promontory 
Bristle in pyramid 
Fenestra rotunda 
Sulcus tympanicus 
Bristle in stylomastoid foramen. 



Fig. 49. — Section through the petrous and mastoid portions of the temporal bone, showing the communication 
of the cavity of the tympanum wiith the mastoid antrum. 

the mastoid is solid throughout. In addition to these pneumatic cells may be 
seen a large, irregular cavity, the mastoid antrum (Figs. 49 and 50), situated at 
the upper and front part of the section. This must be distinguished from the 
mastoid cells, though it communicates with them. The mastoid cells are not 
developed until after puberty, but the mastoid antrum is almost as large at birth 
as it is in the adult bone. The antrum and cells are filled with air, and are lined 
with a prolongation of the mucous membrane of the tympanum, which extends 
into them through an opening, by which they communicate with the cavity of 
the tympanum. 



In consequence of the communication which exists between the tympanum and mastoid cells, 
inflammation of the hning membrane of the former cavity may easily travel backward to that 
of the antrum, leading to caries and necrosis of their walls and the risk of transference of the 
inflammation to the lateral sinus or encephalon. 

The Petrous Portion {pars petrosa [pyramid]) (Fig. 48). — The petrous portion 
is a pyramidal process of bone wedged in at the base of the skull between the 



84 



SPECIAL ANAT03IY OF THE SKELETON 



sphenoid and occipital bones. Its direction from without is inward, forward, 
and a little downward. It presents for examination an apex, four surfaces, and 
four borders, and contains in its interior the essential parts of the organ of hearing. 

Apex {apex pyramidis) . — The apex of the petrous portion, rough and uneven, 
is recei^'ed into the angular interval between the posterior border of the greater 
wing of the sphenoid and the basilar process of the occipital ; it presents the ante- 
rior or internal orifice of the carotid canal (foramen caroticum internum), and 
forms the posterior and external boundary of the foramen lacerum medium. 

Surfaces. — The superior surface of the petrous portion (Fig. 48) forms the 
posterior part of the middle fossa of the skull; it looks upward and forward. 
This surface is continuous with the squamous portion, to which it is united by 




PANIC CANfl 



Fig. 50. — Right temporal bone cut open to show the anterior surface of the petrous portion. X 2. (Spalteholz.) 



a suture, the petrosquamous suture, the remains of which are distinct even at a 
late period of life. 

The superior surface presents five points for examination: (1) An eminence 
(eminentia arcuata) near the centre, which indicates the situation of the superior 
semicircular canal. (2) In front and a little to the outer side of this eminence a 
depression indicating the position of the tympanum; here the layer of bone which 
separates the tympanum from the cranial cavity is extremely thin, and is known 
as the tegmen tympani. The tliin inferior extremity of this plate drops downward 
and presents itself at the inner extremity of the Glaserian fissure, there making 
the fissure double; the anterior slit is called the canal of Huguier, and it transmits 
the chorda tympani nerve. (3) A shallow groove, sometimes double, leading 
outward and backward to an oblique opening, the hiatus Fallopii (liiatus caualis 
facialis), for the passage of the greater petrosal nerve and the petrosal branch of 
the middle meningeal artery. (4) A smaller opening (apertura superior canaliculi 
tympanici), occasionally seen external to the latter, for the passage of the smaller 
petrosal nerve. (5) A shallow depression, the trigeminal depression {impressio 



THE TEMPORAL BONE 



85 




trigemini), for the reception of the Gasserian ganghon, is placed at the inner 
extremity of this surface. 

The anterior or tympanic surface (Fig. 50) is mostly hidden by the tympanic por- 
tion of the bone, and is best studied either in very young skulls or in bones which 
have been cut behind the tympanic membrane. This surface forms the postero- 
internal wall of the tympanum and presents an oval foramen (fenestra ve.stibiili) , 
into which the base of the stapes is fitted. Just above and external to the fenestra 
ovalis is the mastoid antrum, leading from the tympanum to the mastoid cells. 
The antrum is roofed by the tegmen tym- 

pani. Below and internal to the fenestra 2 3 

ovalis is a rounded eminence, the promon- 
tory, formed by the first turn of the cochlea. 
Below the promontory is situated the fe- 
nestra rotunda, which is closed in the recent 
state by a membrane. 

Internal to the fenestra ovalis is the 
orifice of the canal which transmits the 
Tensor tympani; below this is the Eusta- 
chian canal for the passage of air from 
the pharynx to the tympanum. The two 
canals are separated by the processus coch- 
leariformis. On this surface, just above, 
then external to the oval foramen, be- 
tween it and the antrum, is the facial 
canal {canalis facialis). This canal is 
traversed by the facial nerve on its way to 
the stylomastoid foramen. The portion 
of the anterior surface not covered by the 
tympanic plate is occupied by the termina- 
tion of the carotid canal (foramin caroti- 
cum internum), the wall of w'hich is defi- 
cient in front. 

The posterior surface forms the front part 
of the posterior fossa of the skull, and is continuous with the inner surface of the 
mastoid portion of the bone. It presents three points for examination: (1) 
About its centre a large orifice, the meatus auditorius internus {meatus acusticus 
internus), through which pass the facial, auditory and intermediate nerves, 
and the auditory artery. The size of this meatus varies considerably; its margins 
are smooth and rounded, and it leads into a short canal, about one-third inch in 
length, which runs directly outward and is closed by a vertical plate, the lamina 
cribrosa, which is divided by a horizontal crest, the falciform crest {crista transversa), 
into two unequal portions (Fig. 51). Each portion is subdivided by a small 
vertical crest into two parts, named, respectively, anterior and posterior. 
The lower portion presents three sets of foramina : one group just below the pos- 
terior part of the crest, the area cribrosa media, consisting of a number of small 
openings for the nerves of the saccule; below and posterior to this, the foramen 
singulare, or opening for the nerve of the posterior semicircular canal; in front 
and below the first, the tractus spiralis foraminosus, consisting of a number of small, 
spirally arranged openings which terminate in the canalis centralis cochleae and 
transmit the nerve of the cochlea; the upper portion, that above the crista, pre- 
sents behind a series of small openings, the area cribrosa superior, for the passage 
of filaments of the utricle and superior and external semicircular canal, and, in 
front, one large opening, the commencement of the aquaeductus Fallopii {canalis 
facialis), for the passage of the facial nerve. (2) External and below the meatus 



Fig. 5i. — Diagrammatic view of the fundus ol 
the internal auditory meatus: 1, Falciform crest, 
2, Anterior superior cribriform area, 2', Internal 
opening of the aquaeductus Fallopii, 3, Vertical 
crest which ssparates the anterior and posterior 
superior cribriform areas, 4. Posterior superior 
cribriform area, with (4') openings for nerve 
filaments. 5. Anterior inferior cribriform area, 
5'. Spirally arranged, sieve-like openings for the 
nerves to the cochlea. 5". Opening of the cen- 
tral canal of the cochlea. 6, Crest which sepa- 
rates t':c anterior and posterior inferior cribriform 
areas. 7. Posterior inferior cribriform area. 7'. 
Orifices for the branches of the nerve to the 
saccule. 8. Foramen singulare of Morgagni, 
with the anterior portion of the canal which gives 
passage to the nerve to the posterior semicircular 
canal. (Testut.) 



86 SPECIAL ANATOMY OF THE SKELETON 

auditorius is a small slit (apertura externa aquaedudus vestibuli), almost hidden 
by a thin plate of bone, leading to a canal, the aquaeductus vestibuli, which trans- 
mits the ductus endolymphaticus, together with a small artery and vein. (3) In 
the interval between these two openings, but above them, is an angular depression 
{fossa subarcuata.) , which lodges a process of the dura, and transmits a small vein 
into the cancellous tissue of the bone. In the child this depression is represented 
by a large fossa, the floccular fossa, which extends backward as a blind tunnel 
under the superior semicircular canal. 

The inferior or basilar surface (Fig. 52) is rough and irregular, and forms part 
of the base of the skull. Passing from the apex to the base, this surface presents 
the following points for examination: (1) A rough surface, quadrilateral in form, 
which serves partly for the attachment of the Levator palati and Tensor tympani 




STYLOPHARYNGEUS 



Sough quadrilateral surface. _ 

External opening 0/"*'%^ 

carotid canal. -^ 

Canal for Jacobson^s nerve. 

Aquaeductus cochleae. 

Canal for Arnold' a nerve. 

Jugular fossa. 

Vaginal process. 

Styloid process. 
Stylomastoid foramen. 
Jugular surface. 
Auricular fissure. 



Fig. 52. — Petrous portion of the left temporal bone. Inferior surface. 

muscles. (2) The large circular aperture of the carotid canal, the external carotid 
opening (foramen caroticum externum) ; the canal ascends at first vertically, and 
then, making a bend, runs horizontally forward and inward; it transmits the 
internal carotid artery and the carotid sympathetic plexus. Within the carotid 
canal are several openings {canaliculi caroticotympanici) , which transmit tympanic 
branches of the internal carotid artery and of the carotid sympathetic plexus. 
(3) The opening of the aquaeductus cochleae {apertura externa canaliculi cochleae), 
a small, triangular opening, lying on the inner side of the latter, close to the pos- 
terior border of the petrous portion; it transmits a vein from the cochlea, which 
joins the internal jugular. (4) External to these openings a deep depression, the 
jugular fossa {fossa jugularis) , which varies in depth and size in different skulls ; 
it lodges the lateral sinus, and, with a similar depression on the margin of the 
jugular process of the occipital bone, forms the foramen lacerum posterius or 



THE TEMPORAL BONE 87 

jugular foramen. (5) A foramen which is the opening of a small canal (canaliai- 
lu^ tympanicus) for the passage of Jacobson's nerve (the tympanic branch of the 
glossopharyngeal) ; this foramen is seen in front of the bony ridge dividing the 
carotid canal from the jugular fossa. (6) A small foramen on the wall of the 
jugular fossa, for the passage of the auricular branch of the vagus {Arnold's) 
nerve. (7) Behind the jugular fossa a smooth, square-shaped facet, the jugular 
surface; it is covered with cartilage in the recent state, and articulates with the 
jugular process of the occipital bone. (S) The stylomastoid foramen {joravien 
stylomastoidevm) , a rather large orifice, placed between the styloid and mastoid 
processes; it is the termination of the facial canal, and transmits the facial nerve 
and stylomastoid artery. 

Borders. — The posterosuperior border {angulus superior pyramidis), the longest, 
is grooved for the superior petrosal sinus, and has attached to it the tentorium 
cerebelli ; at its inner extremity is a semilunar notch, upon which the fifth nerve 
lies. 

The postero-inferior border is intermediate in length between the postero- 
superior and antero-inferior. Its inner half is marked by a groove, which, when 
completed by its articulation with the occipital, forms the channel for the infe- 
rior petrosal sinus. Its outer half presents a deep excavation, the jugular fossa 
{fossa jugularis), which, with a similar notch on the occipital, forms the foramen 
lacerum posterius. A projecting eminence of bone occasionally stands out from 
the centre of the notch, and divides the foramen into two parts. 

The anterosuperior border is divided into two parts — an outer, joined to the 
squamous portion by a suture, the remains of which are distinct; an inner, free, 
articulating with the spinous process of the sphenoid. At the angle of junction 
of the petrous and squamous portions is seen the opening of the canalis viuscvlo- 
tuharius. 

The antero-inferior border is also divided into two parts — the outer portion is 
hidden from view by the tympanic plate. The inner part is free and forms the 
inferior lip of the carotid canal and gives attachment to the Tensor tympani and 
Levator palati muscles. 

The Tympanic Portion {pars tympanica). — The tympanic portion is placed in 
front of the anterior surface of the petrous portion; its most internal part is 
narrow and forms the anterior wall of the Eustachian canal. Externally it 
broadens out and has an antero-inferior and a posterosuperior surface, an 
anterosuperior, an antero-inferior, and an external border. The antero-inferior 
surface looks forward and downward and forms the posterior part of the glenoid 
fossa. The posterosuperior surface forms the anterior wall of the external audi- 
tory canal. From this surface there continues on to the anterior part of the 
mastoid portion a U-shaped process, with its concavity upward; this process 
shares in forming the inferior and posterior wall of the external auditory canal. 
Between the upturned part of the U-shaped process and the mastoid is a foramen 
(fissura tympanoviastoidea) transmitting the tympanic (auricular nerve of Arnold) 
branch of the vagus. In the concavity of this U-shaped process is a furrow 
{sidcus tympanicus), in which is placed the tympanic membrane {membrana 
tympani), like a mirror in its frame. The anterosuperior border fuses with the 
middle zygomatic root. Internally, this border is continuous with the upper 
border of the narrow part of the bone, and is separated from the squamous 
portion of the bone by the Glaserian fissure and a small part of the tegmen 
tympani. The antero-inferior border is thin internally; externally it divides into 
two laminse and ensheaths the root of the styloid process — hence the name 
vaginal process given to this border. The external border is free and rough, and 
has attached to it the cartilaginous part of the ear. 

The glenoid fossa {fossa mandibular is) is a considerable hollow formed in front 



SPECIAL ANATOMY OF THE SKELETON 



by the squamous part of the temporal, and behind by the tympanic bone. The 
part of the fossa formed by the squamous portion is covered with cartilage and 
articulates with the condyle of the mandible. The posterior part of the fossa lodges 
part of the parotid gland, and is formed by the antero-inferior surface of the tym- 
panic portion. The fossa is crossed by an oblique fissure, the petrotympanic fissure 
(Glaserian fissure), which leads into the tympanum, lodges the processus gracilis 
of the malleus, and transmits the tympanic branch of the internal maxillary 
artery. This fissure is closed externally; at its inner extremity it is separated 
from the squamous portion by the downgrowth of a process of bone from the 
tegmen tympani {^processus inferior tegmini tympani) of the petrous portion 
between the squamous and tympanic plates, making the fissure at its internal 
extremity a double one. The anterior limb is known as the canal of Huguier 
{canaliculus chordae tympani), and transmits the chorda tympani nerve. 

The external auditory meatus is bounded in front, below, and behind by the 
tympanic portion. The roof and the upper part of the posterior wall are formed 
by the squamous portion. The canal is about three-quarters of an inch (18 mm.) 
in length, and is directed inward and forward. In vertical section it is of oval 
outline, the long axis of the oval being vertical in the outer segment and oblique 
in the inner segment. 

The styloid process is a sharp spine of varying length. It projects downward 
and forward from the vaginal process of the tympanic part, and gives origin 
to the stylohyoid and stylomandibular ligaments, and to the Styloglossus, Stylo- 
pharyngeus, and Stylohyoid muscles. 

Structure. — The squamous portion is like that of the other cranial bones; the mastoid portion, 
cellular; and the petrous portion, dense and hard. 

Development (Fig. 53). — The temporal bone is developed from ten centres, exclusive of those 
for the internal ear and the ossicles — viz., one for the squamous portion, including the zygoma, 

one for the tympanic plate, six for the petrous 
and mastoid parts, and two for the styloid 
process. Just before the close of fetal life 
the temporal bone consists of four parts: 
(1) The squamozygomatic part, ossified in 
membrane from a single nucleus, 'n'hich 
appears at its lower part about the second 
month. (2) The tympanic plate, an imper- 
fect ring, in the concavity of which is a 
groove, the sulcus tympanicus, for the at- 
tachment of the circumference of tlie tym- 
panic membrane. This is also ossified from 
a single centre, which appears in membrane 
about the third month. (3) The petromas- 
toid part, which is developed from six centres, 
appearing in the cartilaginous ear capsule 
about the fifth or sixth month. Four of these 
are for the petrous portion and are placed 
around the labyrinth, and two are for the 
mastoid (Vrolik). According to Huxley, the 
centres are more numerous and are disposed 
so as to form three portions: The first por- 
tion includes most of the labyrinth (part of 
the cochlea, vestibule, superior semicircular 
canals, and the inner wall of the tympanic 
cavity) and a part of the petrous and mastoid. 
This portion he has named the pro-otic. The second portion — the opisthotic — consists of the rest 
of the petrous, and is thus made up: the floor of the tympanum and vestibule surrounds the caro- 
tid canal and the outer and lower portions of the cochlea and spread inward below the internal 
auditory meatus. The third portion — the pteriotic — roofs the antrum and tympanic cavity. 
The fourth portion — the epiotic — includes the remainder of the mastoid. The petromastoid 
is ossified in cartilage. (4) The styloid process is also ossified in cartilage from two centres — 
one for the base, which appears before birth, and is termed the tympanohyal ; the other, comprising 




JS' 



6 for petrous 

and mastoid 

portioiis. 



2' for styloid p 
Fio. 53. — Developmi 



THE SPHENOID BONE 



89 



the rest of the process, is named the stylohyal, and does not appear until after birth. Shortly 
before birth the tympanic plate unites with the squamous. Tlie petrous and mastoid unite at 
puberty, and in some slculls never becomes united. The subsequent changes in this bone are, 
that the tympanic plate e.\tends outward and backward, so as to form the meattis auditorius. 
(1) The extension of the tympanic plate, however, does not take place at an equal rate all around 
the circumference of the ring, but occurs most rapidly on its anterior and posterior portions, 
and these outgrowths meet and blend, and thus, for a time, there exists in the floor of the meatus 
a foramen, the foramen of Huschke; this foramen, usually closed by the fifth year, may persist 
throughout life. (2) The glenoid cavity is at first extremely shallow, and looks outward as 
well as downward; it becomes deeper and is ultimately directed downward. Its change in direc- 
tion is accounted for as follows: the part of the squamous temporal which supports it lies at first 
hclmc the level of the zygoma. As, however, the base of the skull increases in width, this lower 
part of the squama is directed horizontally inward to contribute to the middle fossa of the skull, 
and its surfaces therefore come to look upward'and downward. (3) The mastoid portion is 
at first quite flat, and the stylomastoid foramen and rudimentary styloid process lie immediately 
behind the tympanic ring. With the development of the air cells the outer part of the mastoid 
portion grows downward and forward to form the mastoid process, and the styloid process 
and stylomastoid foramen now come to lie on the under surface. The descent of the foramen 
is necessarily accompanied by a corresponding lengthening of the aqueduct of Fallopius. 



Squamozis portion 



Petrosqua7nous 
sutute 



Squamous portion 

Peirosquonnous suture 
Eimneniia arcuata, 




Fig. 54. — Temporal bone at birth. Outer aspect. 



Fossa subarcuaia 
Meatus acusticus internus 
Fig. 55. — Temporal bone at birth. Inner aspect. 



(4) The downward and forward growth of the mastoid process also pushes forward the tympanic 
plate, so that the portion of it which formed the original floor of the meatus and containing 
the foramen of Huschke is ultimately found in the anterior wall. (5) With the gradual increase 
in size of the petrous portion the floccular fossa or tunnel under the superior semicircular canal 
becomes filled 'up and almost obliterated. 

Articulations. — With Jive bones — occipital, parietal, sphenoid, mandible, and malar. 

Attachment of Muscles.— To fifteeen—to the squamous portion, the Temporal; to the 
zygoma, the Masseter; to the mastoid portion, the Occipitofrontalis, Sternomastoid, Splenius 
<;apitis, Trachelomastoid, Digastric, and Posterior auricular; to the styloid process, the Stylo- 
pharyngeus, Stylohyoid, and Styloglossus; and to the petrous portion, the Levator palati, Tensor 
tympani. Tensor palati, and Stapedius. 



The Sphenoid Bone (Os Sphenoidale). 



The sphenoid bone is situated at the anterior part of the base of the skull, 
articulating with all the other cerebral cranial bones, which it binds firmly and 
solidly together. In its form it somewhat resembles a bat with its wings extended ; 
and is divided into a central portion or body, two greater and two lesser wir.gs 



90 



SPECIAL ANATOMY OF THE SKELETON 



extending outward on each side of the body, and two processes — the pterygoid 
processes — which project from the lower part of this body. 

The Body {corpus). — The body is of large size and hollowed out in its interior 
so as to form a mere shell of bone. It presents for examination four surfaces — 
a superior, an inferior, an anterior, and a posterior. 

Surfaces. — The superior surface (Fig. 56) presents in front a prominent spine, 
the ethmoidal spine, for articulation with the cribriform plate of the ethmoid; 
behind this is a smooth surface having in the median line a slight longitudi- 
nal eminence, with a depression on each side for the lodgment of the olfac- 
tory lobes. This surface is bounded behind by a ridge, which forms the ante- 
rior border of a narrow, trans^'erse groove, the optic groove {sulnis chiasmatis) ; 
behind the ridge lies the optic chiasm ; the groove is continuous on each side with 
the optic foramen (foramen opticum) ,ioT the passage of the optic nerve and ophthal- 
mic artery. Behind the optic groove is a small eminence, olive-like in shape, the 



Middle chnoid process. 
Posterior dinoid process. 



Ethmoidal 




Optic foramen. 

Sphenoidal fissure 

Foramen rotundum. 

Foramen Vesalii: 

Foramen oval^: 

Foramen spinosum. 



Fig. 56 — Sphenoid bone. Superior surface. 



olivary eminence (tuberculum sellae) ; and still more posteriorly a deep depression, 
the sella turcica (fossa hypophyseos) , which lodges the circular sinus and the 
hypophysis. This fossa is perforated by numerous foramina, for the transmission 
of nutrient vessels into the substance of the bone. It is bounded in front by the 
olivary eminence, and also by two small processes, one on either side, called the 
middle clinoid processes (processus clinoidei medii), which are sometimes connected 
by a spiculum of bone to the anterior clinoid processes. It is bounded behind by 
a square-shaped plate of bone, the dorsum sellae, terminating at each superior 
angle in a tubercle, the posterior clinoid process (processus clinoideus posterior'). 
The size and form of these processes vary considerably in different individuals. 
They deepen the sella turcica, and serve for the attachment of prolongations 
from the tentorium cerebelli. The sides of the dorsum sellae are notched for 
the passage of the abducent nerves, and below present a sharp process, the 
petrosal process, which is joined to the apex of the petrous portion of the temporal 
bone, forming the inner boundary of the middle lacerated foramen. Behind 
this plate the bone presents a shallow depression, which slopes obliquely backward, 
and is continuous with the basilar groove of the occipital bone; it is called the 
clivus, and supports the upper part of the pons. On either side of the body is 



THE SPHENOID BONE 



91 



a broad, /-shaped groove, which lodges the internal carotid artery and the 
cavernous sinus. (See page 724 for other structures in the sinus.) It is called 
the cavernous groove {sulcus caroiicus). Along the outer margin of this groo\'e, 
at its posterior part, is a ridge of bone in the angle between the body and greater 
wing, called the lingula (lingula sphenoidalis). 

The posterior surface, quadrilateral in form, is joined to the basilar process 
of the occipital bone. During childhood these bones are separated by a layer 
of cartilage; but later (between the eighteenth and twenty-fifth years) this becomes 
ossified from above downward, and the two bones then form one piece. 

The anterior surface (Fig. 57) presents, in the median line, a vertical ridge of 
bone, the ethmoidal crest {crista sphenoidalis), which articulates in front with the 
perpendicular plate of the ethmoid, forming part of the septum of the nose (Fig. 
57). On either side of it are irregular openings leading into the sphenoidal sinuses 
(sinus sphenoidales), which are two large, irregular cavities of the hollowed out 
interior of the body of the sphenoid bone, and separated more or less completely 
from each other by a perpendicular bony septum {septum sinuuvi sphenoidalium). 
Occasionally they extend into the basilar process of the occipital nearly as far 
as the foramen magnum. Their form and size vary considerably; they are seldom 




Flerygoid ridge 



Jiiternal pterygoid plate. 
Hamv.lar process. 



symmetrical, and are often partially subdivided by irregular, osseous laminae. 
One or both sinuses may be absent. The septum is seldom quite vertical, being 
commonly bent to one or the other side. These sinuses do not exist in very 
young children, but appear, according to Laurent, in the seventh year. After 
once appearing they increase in size as age advances. They are partially closed, 
in front and below, by two thin, curved plates of bone, the sphenoidal turbinated 
processes {conchae sphenoidales). At the upper part of each is a round opening 
{aperttira sinus sphenoidalis), by which the sinus communicates with the upper 
and back part of the nose, and occasionally with the posterior ethmoidal cells 
or sinuses. The lateral margins of the surface present a serrated edge, which 
articulates with the os planum of the ethmoid, completing the posterior ethmoidal 
cells; the lower margin, also rough and serrated, articulates with' the orbital 
process of the palate bone. 

The inferior surface presents, in the middle line, a triangular spine, the rostrum 



92 SPECIAL ANA TOMV OF THE SKELETON 

(rostrum sphenoidalis), which is continuous with the sphenoidal crest on the 
anterior surface, and is received into a deep fissure between the altie of the vomer. 
On each side may be seen a projecting lamina of bone, the vaginal process (pro- 
cessus vaginalis), which runs horizontally inward from near the base of the ptery- 
goid process and articulates with the edges of the vomer. Close to the root of 
the pterygoid process is a groove (sulcus plerygopalatinus), formed into a com- 
plete canal when articulated with the sphenoidal process of the palate bone; it 
is called the pterygopalatine canal, and transmits the pterygopalatine vessels 
and a pharyngeal branch of the sphenopalatine ganglion. 

The Greater or Temporal Wings {alae magna) . — The greater wings are two 
strong processes of bone which arise from the sides of the body, and are curved 
in a direction upward, outward, and backward, each being prolonged behind 
into a sharp-pointed extremity, the alar, or sphenoidal spine (spina angidaris). 
Each wing presents three surfaces and a circumference. 

Surfaces. — The superior surface (fades cerebralis) (Fig. 56) forms part of 
the middle fossa of the skull; it is deeply concave, and presents eminences and 
depressions for the convolutions of the cerebrum. At its anterior and internal 
part is seen a circular aperture, the foramen rotundum, for the transmission of 
the second division of the trigeminal nerve. Behind and external to this is a 
large oval foramen, the foramen ovale, for the transmission of the third division 
of the trigeminal nerve, the small meningeal artery, and sometimes the small 
petrosal nerve. At the inner side of the foramen ovale a small aperture may 
occasionally be seen opposite the root of the pterygoid process; it is the foramen 
Vesalii, transmitting a small vein. In the posterior angle, near to the spine of 
the sphenoid, is a short canal, sometimes double, the foramen spinosum, which 
transmits the middle meningeal artery and the meningeal branch of the superior 
maxillary nerve. Just to the inner side of the foramen spinosum a minute fora- 
men (canaliculus innominatum) is occasionally found, for the passage of the small 
petrosal nerve. 

The external surface (Fig. 57) is convex and divided by a transverse ridge, 
the pterygoid ridge (crista infratemporalis), into two portions. The superior 
or larger, convex from above downward, concave from before backward, enters 
into the formation of the temporal fossa, and gives attachment to part of the 
Temporal muscle. The inferior portion, smaller in size and concave, enters 
into the formation of the zygomatic fossa, and affords attachment to the External 
pterygoid muscle. It presents, at its posterior part, a sharp-pointed eminence 
of bone, the spine, to which are connected the internal lateral ligament of the 
mandible and the Tensor palati muscle. At its inner and anterior extremity is 
a triangular spine of bone, which serves to increase the extent of origin of the 
External pterygoid muscle. 

The anterior surface is divided into two parts, the orbital surface above and the 
sphenomaxillary below. The orbital surface is quadrilateral in form; it looks 
inward and forward, and assists in forming the outer wall of the orbit. It 
is bounded above by a serrated edge for articulation with the frontal bone. 
Internally this edge is sharp and free and forms the lower boundary of the 
sphenoidal fissure. At about the centre of the free part of this border a little 
tubercle projects, giving origin to one head of the External rectus muscle of the 
eyeball. At its outer part is a notch for the transmission of a recurrent branch 
of the lacrimal artery. The outer border is serrated for articulation with the 
malar bone. The lower border is rounded and enters into the formation of the 
sphenomaxillary fissure. This border separates the orbital surface above from 
the sphenomaxillary portion below. This latter portion is situated just above 
the pterygoid process and helps to form the posterior wall of the sphenomaxillary 



THE SPHENOID BONE 



93 



fossa in the articulated skull and exhibits the anterior extremity of the foramen 
rotundum. 

Circumference (Fig. 56). — Commencing from behind, that portion of the circum- 
ference of the body of the sphenoid to the spine is serrated and articulates by its 
outer half with the inner part of the antero-superior border of the petrous portion 
of the temporal bone, while the inner half forms the anterior boundary- of the mid- 
dle lacerated formaen, and presents the posterior aperture of the Vidian canal 
{canalis pterygoideus) , for the passage of the Vidian nerve and artery. In front 
of the spine, the circumference of the greater wing presents a serrated edge, 
bevelled at the expense of the inner table below and of the external above, which 
articulates with the squamous portion of the temporal bone. At the tip of the 
greater wing a triangular portion is seen, bevelled at the expense of the internal 
surface, for articulation with the anterior inferior angle of the parietal bone. 
Internal to this is a triangular, serrated surface, for articulation with the frontal 




Posterior view. 



bone ; this surface is continuous internally with the sharp inner edge of the orbital 
plate, which assists in the formation of the sphenoidal fissure, and externally 
with the serrated margin for articulation with the malar bone. 

The Lesser or Orbital Wings {alae parvae). — The lesser wings are two thin 
triangular plates of bone which arise, one on each side, from the upper part of the 
lateral surface of the body of the sphenoid, and, projecting transversely outward, 
terminate in a sharp point (Fig. 56). The superior surface of each forms part of 
the anterior fossa of the skull, is smooth, flat, broader internally than externally, 
and supports part of the frontal lobe of the cerebrum. The inferior surface 
forms the back part of the roof of the orbit and the upper boundary of the sphenoi- 
dal fissure, or foramen lacerum anterius. This fissure is of a triangular form, and 
leads from the cavity of the cranium into the orbit. It transmits the third, the 
fourth, the three branches of the ophthalmic di^■ision of the trigeminal, the 
abducent nerve, some filaments from the cavernous plexus of the sympathetic, the 
orbital branch of the middle meningeal artery, a recurrent branch from the lacri- 
mal artery to the dura and the ophthalmic vein. The anterior border of the lesser 



94 



SPECIAL ANATOMY OF THE SKELETON 



wing is serrated for articulation with the frontal bone ; the posterior border, smooth 
and rounded, is received into the sylvian fissure of the cerebrum. The inner 
extremity of this border forms the anterior clinoid process {processus dinoideus 
anterior). The lesser wing is connected to the side of the body by two roots, the 
upper thin and flat, the lower thicker, obliquely directed, and presenting on its 
outer side, near its junction with the body, a small tubercle, for the attachment 
of the common tendon of origin of three of the Extrinsic muscles of the eye. Be- 
tween the two roots is the optic foramen, for the transmission of the optic nerve 
and ophthalmic artery. 

The Pterygoid Processes {-processus pterygoidei). — ^The pterygoid processes, 
one on each side, descend perpendicularly from the place where the body and 
greater wing unite (Fig. 59). Each process consists of an external and an in- 
ternal plate, which are joined together by their anterior borders above, but 
are separated below, leaving an angular cleft, the pterygoid notch, in which the 
pterygoid tuberosity of the palate bone is received. The two plates diverge 
from each other from their line of connection in front, so as to form in conjunc- 
tion with the tuberosity of the palate bone a V-shaped fossa, the pterygoid fossa. 
The external pterygoid plate {laviina lateralis processus pterygoidei) is broad and 




Fig. 59. — Sphenoid bone. Posterior surface. 



thin, turned a little outward, and, by its outer surface, forms part of the inner wall 
of the zygomatic fossa, giving attachment to the External pterygoid; its inner sur- 
face forms part of the pterygoid fossa, and gives attachment to the Internal 
pterygoid. The posterior border of this plate frequently has one or more rough 
projections, to one of which is attached the pterygospinous ligament, when this is 
present. The internal pterygoid plate {lamina medialis processus pterygoidei) is 
much narrower and longer, curving outward, at its extremity, into a hook-like 
process of bone, the hamular process {haviulii-s pterygoideus) , around which turns 
the tendon of the Tensor palati muscle. The outer surface of this plate forms 
part of the pterygoid fossa, the inner surface forming the outer boundary of the 
posterior aperture of the nares. The posterior border of this plate gives attach- 
ment to the phar.yngeal aponeurosis throughout its entire length. The Superior 
constrictor muscle of the pharynx arises from its lower half. Projecting back- 
ward from the middle of this border is a spine {processus tuharius), which supports 
the pharyngeal end of the Eustachian tube. Above this the border divides into 
two lips; the space between is the scaphoid fossa ( fossa scaphoidea). In this fossa 
arises the Tensor palati muscle. The anterior margin articulates with the poste- 
rior border of the perpendicular plate of the palate bone. 

Superiorly, the internal pterygoid plate has a thin lamina of bone, the vaginal 



THE SPHENOID BOXE 



95 



process {processus vagiiialis), which runs inward on the under surface of the body of 
the sphenoid nearly to tlie rostrum. In the groove between the two in the articu- 
lated skull are seen the alae of the vomer. On the under surface of the vaginal 
process is a groove (svlciis pterygopalatimos), which in the articulated skull is con- 
verted into the pterygopalatal canal by union with the sphenoidal process of the 
palate bone. At the junction of the vaginal process and the inner plate is the 
pterygoid tubercle, just above which is the posterior opening of the Mdian canal. 
The anterior surface of the pterygoid process is quite broad at its base, and forms 
the chief part of the posterior wall of the sphenomaxillary fossa. 

The Sphenoidal Turbinated Processes (conchae sphenoidales). — The sphe- 
noidal turbinated processes are two thin curved plates of bone, which exist as 
separate pieces until puberty, and occasionally are not joined to the sphenoid 
in the adult. They are situated at the anterior part of the body of the sphe- 
noid, an aperture (aperiura sinus sjjhcnoidalis) of \ariable size being left in 
the anterior wall of each, through which the sphenoidal sinuses open into the 
nasal fossse. They are irregular in form and taper to a point behind, being 
broader and thinner in front. Their upper surface, which looks toward the 
cavity of the sinus, is concave; their under surface convex. Each bone articulates 
in front with the ethmoid, externally with the palate; its pointed posterior 
extremity is placed above the vomer, and is received between the root of 
the pterygoid process on the outer side and the rostrum of the sphenoid on the 
inner.' 

Development. — Up to about the eighth month of fetal life the sphenoid bone consists of two 
distinct parts — a posterior or postsphenoid part, which comprises the sella turcica, the greater 
wings, and the pterygoid processes; and an anterior or presphenoid part, to which the anterior 
part of the body and lesser wings belong. It is developed (ram fourteen centres — eight for the 
postsphenoid division and six for the presphenoid. All parts except the internal pterygoid 
plates have an intracartilaginous origin. 

Postsphenoid Division. — The first nuclei to appear are those for the greater wings (alt- 
sphenoids). They make their appearance between the foramen rotundum and foramen ovale 
about the eighth week, and from them the external pterygoid plates are also formed. Soon after, 
the nuclei for the posterior part of the body appear, one on either side of the sella turcica, and 
become blended together aljout the middle of fetal life. About the ninth or tenth week the 
centre for the internal pterygoid plate appears, followed by the centre for the hamiilar process; 
the centre for the lingula appears during the fourth month, and soon joins the rest of the body. 
The internal and external pterygoid plates become joined at about the sixth month. 

one for each two for anterior 
lesser wing, part of body. 




one for each tntemat - 
pterygoid plate 

one for /»' «««'' hngula v 

each greater wing and external ptery- 
[_goid plate, 
one/or each Sphenoidal turbinated process. 



Fig. 61. — Sphenoid bone at birth. Posterior aspect. 



Presphenoid Division. — The first nuclei to appear are those for the lesser wings (orbito- 
phenoids). They make their appearance about the ninth week, at the outer borders of the optic 



* -A. small portion of the sphenoidal turbinated process sometimes enters into the formation of the inner 
wall of the orbit, between the os planum of the ethmoid in front, the orbital plate of the palate below, and 
the frontal above. — Cleland, Roy. Soo. Trans., 1862. 



96 



SPECIAL ANATOMY OF THE SKELETON 



foramina. A second pair of nuclei appears on the inner side of the foramina shortly after, and, 
becoming united, form the front part of the body of the bone. The remaining two centres for 
the sphenoidal turbinated processes make their appearance about the fifth month. At birth they 
consist of small triangular laminse, and it is not until the third year that they become hollowed out 
and cone-shaped. About the fourth j-ear they become fused with the lateral masses of the 
ethmoid, and between the ninth and twelfth years they unite with the sphenoid bone. 

The presphenoid is united to the body of the postsphenoid about the eighth month, so that at 
birth the bone consists of three pieces — viz., the body in the centre, and on each side the great 
wings with the pterygoid processes. The lesser wings become joined to the body at about the 
time of birth. During the first year after birth the greater wings and l:>ody are united. From 
the ninth to the twelfth year the turbinated processes are partially united to the sphenoid, their 
junction being complete by the twentieth year. Lastly, the sphenoid joins the occipital from the 
eighteenth to the twenty-fifth year. 

Articulations. — The sphenoid articulates with all the bones of the cerebral cranium, and 
five pf the face — the two malar, the two palate, and vomer; the exact extent of articulation with 
each bone is shown in the accompanying figures.' 

Attachment of Muscles. — To elemn pairs — the Temporal, External pterygoid, Internal 
pterygoid, Superior constrictor, Tensor palati, Levator palpebrae, Superior oblique, Superior 
rectus. Internal rectus, Inferior rectus. External rectus. 

The Ethmoid Bone (Os Ethmoidale) . 

The ethmoid is an exceedingly light, spongy bone, of a cubical form, situated 
at the anterior part of the base of the cranium proper, between the two orbits 
at the root of the nose, and contributing to the formation of each of these cavi- 
ties. It consists of four parts — a horizontal plate, which forms part of the base 
of the cranium proper; a perpendicular plate, which forms part of the septum of 
the nose; and two lateral masses, containing a number of spaces. 




Slit for nasal nerv& 

Anterior ethmoidal cells 



Vertical plate 
{lamina perpendicularis) 



Unciform process 



Fig. 62. — Ethmoid bone. Outer surface of right lateral mass. (Enlarged.) 

The Horizontal Lamina, or Cribriform Plate {lamina cribrosa) (Fig. 62), forms 
part of the anterior fossa of the base of the skull, and is received into the eth- 
moid notch of the frontal bone between the two orbital plates. Projecting up- 
ward from the middle line of this plate is a thick, smooth, triangular process of 
bone, the crista galli. Its base joins the cribriform plate. Its posterior border, 
long, thin, and slightly curved, serves for the attachment of the falx cerebri. Its 
anterior border, short and thick, articulates with the frontal bone, and presents 
two small projecting alse {'processus alares), which are received into corresponding 
depressions in the frontal, completing the foramen cecum behind. Its sides are 
smooth and sometimes bulging, in which case it is found to enclose a small sinus. 
On each side of the crista galli the cribriform plate is narrow and deeply grooved, 
to support the bulb of the olfactory tract, and is perforated by foramina for the 
passage of the olfactory nerves. These foramina are arranged in three rows: 
The innermost, which are the largest and least numerous, are lost in grooves on the 

lit also sometimes articulates with the tuberosity of the maxilla. 



THE ETHMOID BONE 



97 



upper part of the septum ; the foramina of the outer row are continued on to the 
surface of the superior turbinated process. The foramina of the middle row 
are the smallest; they perforate the bone and transmit nerves to the roof of the 
nose. At the front part of the cribriform plate, on each side of the crista galli, is 
a small fissure, which transmits the nasal branch of the ophthalmic nerve; and 
at its posterior part a triangular notch, which receives the ethmoidal spine of the 
sphenoid. 



Cnsta galh 






Lamina crihrosa 




Lateral 7ii.ass 



Superior turhina ted 

process 
Superior meatus 

Piocessus uncinaius 



Biferior turbinated process 
Perpendicular plate 



Fig. 63. — Ethmoid bone from behind. 




Fig. 64. — Ethmoid bo 



(Spalteholz.) 



icitli EtlimoKfa/ 



The Vertical Plate {lamina perpendicular is) (Fig. 65) is a thin, flattened, 
lamella of bone, which descends from the under surface of the cribriform plate, 
and assists in forming the septum of the nose. It is much thinner in the middle 
than at the circumference, 
and is generally deflected 
a little to one side. Its 
anterior border articulates 
with the nasal spine of the 
frontal bone and crest of 
the nasal bones. Its pos- 
terior border, divided into 
two parts, articulates by 
its upper half with the 
sphenoidal crest of the 
sphenoid, by its lower 
half with the vomer. The 
inferior border serves for 
the attachment of the 
triangular cartilage of the 
nose. On each side of 
the perpendicular plate 
numerous grooves are seen, 

leading from the foramina on the cribriform plate; they lodge filaments of the 
olfactory nerves. 

The Lateral Mass, or Labyrinth (labyrinthus ethmoidalis), of the ethmoid 
consists of a number of thin-walled cellular cavities, the ethmoidal cells (celhdae 
ethvioidales), interposed between two vertical plates of bone, the outer one of which 
forms part of the orbit, and the inner one part of the outer wall of the nasal fossa 




Fig. 65. — Perpendicula 



■ plate of ethmoid (enlarged) , showr 
the right lateral mass. 



98 



SPECIAL ANA TO MY OF THE SKELETON 




Fig. 66. — Ethmoid bone. Inner surface of right lateral 



of the corresponding side. There are two lateral masses, one on each side. The 
ethmoidal cells are not present at birth, but appear during the fifth year. In the 
disarticulated bone many of these cells appear to be broken ; but when the bones are 
articulated they are closed in at every part, except where they open into the nasal 
fossae. The upper surface of each lateral mass presents a number of apparently 
half-broken cellular spaces; these are closed in, when articulated, by the edges of 
the ethmoidal notch of the frontal bone. Crossing this surface are two grooves 
on each side, converted into canals by articulation with the frontal; they are the 
anterior and posterior ethmoidal canals (canalis ethmoidale anterius et posterius), 
and open on the inner wall of the orbit. The anterior transmits the nasal nerve 
and the anterior ethmoidal vessels; the posterior transmits the posterior ethmoidal 
A'essels. . The posterior surface also presents large irregular cellular cavities, which 
are closed in by articulation with the sphenoidal turbinated processes and the orbi- 
tal process of the palate. The cells at 
the anterior surface are completed by 
the lacrimal bone and nasal process of 
the maxilla, and those below also by 
the maxilla. The outer surface of each 
lateral mass consists chiefly of a thin, 
smooth, oblong plate of bone, called 
the OS planum (lamina papyracea); it 
forms part of the inner wall of the orbit, 
and articulates, above, with the orbital 
plate of the frontal; helow, with the 
maxilla; in front, with the lacrimal; 
and behind, with the sphenoid .and 
orbital process of the palate. In 
front of the os planum are found the anterior ethmoidal cells, which are completed 
by the lacrimal bone and the nasal process of the maxilla. 

From the inferior part of each lateral mass, immediately beneath the os 
planum, there projects downward and back'ward an irregular hook-like lamina 
of bone, called the unciform process (processus uncinatus); it serves to close in 
the upper part of the orifice of the antrum (Fig. 71), and articulates with the 
ethmoidal process of the turbinated bone. It is often broken in disarticulating 
the bones. 

The inner surface of each lateral mass forms part of the outer wall of the nasal 
fossa of the corresponding side. It is formed of a thin lamella of bone, which 
descends from the under surface of the cribriform plate, and terminates below in 
a free, convoluted margin, the middle turbinated process (concha nasalis media). 
The whole of this surface is rough and marked above by numerous grooves, which 
run nearly vertically downward from the cribriform plate; they lodge branches 
of the olfactory nerve, which are distributed on the mucous membrane covering 
the bone. The back part of this surface is subdivided by a narrow oblique fissure, 
the superior meatus of the nose, bounded above by a thin, curved plate of bone, 
the superior turbinated process (concha nasalis superior). By means of an orifice 
at the upper part of this fissure the posterior ethmoidal cells open into the superior 
meatus. Below, and in front of the superior meatus, is seen the convex surface 
of the middle turbinated process. It extends along the whole length of the inner 
surface of each lateral mass. The middle of its lower margin is free and thick. 
The anterior portion articulates with the superior turbinated crest of the nasal 
process of the maxilla, and the posterior portion articulates with the superior tur- 
binated crest of the maxilla and palate bone. Its concavity, directed outward, 
assists in forming the middle meatus. It is by a large orifice at the upper and 



THE NASAL BONES 99 

front part of the middle meatus that the anterior ethmoidal cells, and through 
them the frontal sinuses, communicate with the nose by means of a funnel- 
shaped canal, the infundibulum {infundihulum ethnoidale) (Fig. 62). The cell- 
ular cavities of each lateral mass, thus walled in by the os planum in the outer 
side and by the other bones already mentioned, are divided by a thin trans- 
verse bony partition into two sets, which do not communicate with each other; 
they are termed the anterior and posterior ethmoidal sinuses. The former, more 
numerous, communicate with the frontal sinuses above and the middle meatus; 
below by means of the infundibulum; the posterior, less numerous, open into 
the superior meatus and communicate (occasionally) with the sphenoidal sinuses. 
In some cases the ethmoidal sinuses communicate with the maxillary sinus. 
In some cases the os planum never develops, and the ethmoidal sinuses are 
separated from the orbit merely by membrane. 

Development. — The ethmoid is developed in cartilage from three centres — one for the per- 
pendicular lamella, and one for each lateral mass. The lateral masses are first developed, 
ossific granules making their appearance in the os planum between the fourth and fifth months 
of fetal life, and extending into the turbinated processes. At birth the bone consists of the two 
lateral masses, which are small and poorly developed. During the first year after birth the 
perpendicular plate and crista galli begin to ossify, from a single centre, and become joined to the 
lateral masses about the beginning of the second year. The cribriform plate is ossified partly 
from the perpendicular plate and partly from the lateral masses. The formation of the ethmoidal 
cells, which completes the bone, does not commence until the end of the fourth year. 

Articulations. — With thirteen bones — the sphenoid, the frontal, and eleven of the face, the 
two nasal, two palate, two maxillse, two lacrimal, two turbinated, and the vomer. No muscles 
are attached to this bone. 

THE BONES OF THE FACE (OSSA FACIEI). 

The facial bones are fourteen in number — viz., the 

Two nasal. Two palate. 

Two maxillse. Two turbinated. 

Two lacrimal. Vomer. 

Two malar. Mandible. 



The Nasal Bones (Ossa Nasalia). 

The nasal bones are two small oblong bones, varying in size and form in dif- 
ferent individuals; they are placed side by side at the middle and upper part of 
the face, forming by their junction "the bridge" of the nose (Fig. 67). Each 
bone presents for examination two surfaces and four borders. 

Surfaces. — The outer surface is concave from abo\'e downward, convex from 
side to side; it is covered by the Pyramidalis and Compressor nasi muscles. It 
is marked by numerous small arterial furrows, and perforated about its centre 
by a foramen {foramen nasale), sometimes double, for the transmission of a 
sinall vein. 

The inner sm'face is concave from side to side, convex from above downward, 
in which direction it is traversed by a longitudinal groove (sometimes a canal), 
for the passage of a branch of the nasal nerve. 

Borders. — The superior border is narrow, thick, and serrated, for articulation 
with the nasal notch of the frontal bone. 

The inferior border is broad, thin, sharp, inclined obliquely downward, out- 
ward, and backward, and serves for the attachment of the lateral cartilage of 
the nose. This border presents, about its middle, a notch, through which passes 



100 



SPECIAL ANATOMY OF THE SKELETON 



the branch of the nasal nerve above referred to, and is prolonged at its inner 
extremity into a sharp spine, which, when articulated with the opposite bone, 
forms the nasal angle. 

The external border is serrated, bevelled at the expense of the internal surface 
above and of the external below, to articulate with the nasal process of the 
maxilla. 



Mic. with malar. 




Groove for 
nasal nerve 



Inner Surface. 

Fig. 69.— Left nasal bone 



The internal border, thicker 
above than below, articulates 
with its fellow of the opposite 
side, and is prolonged behind 
into a vertical crest, which 
forms part of the septum of the 
nose; this crest articulates from 
above downward with the nasal 
spine of the frontal, the per- 
pendicular plate of the eth- 
moid, and the triangular septal 
cartilage of the nose. 



Development. — Of intramembranous origin and from one centre for each bone, which 
appears about the eighth week. 

Articulations. — With four bones — two of the cerebral cranium, the frontal and ethmoid, 
and two of the face, the opposite nasal and the maxilla. 

The nasal bone has no muscles attached to it. 



The Maxillae (Upper Jaw). 

The maxillae are the largest bones of the face, excepting the mandible, and 
form, by their union, the whole of the upper jaw. Each maxilla assists in the 
formation of the walls of three cavities, the roof of the mouth, the floor and 
outer wall of the nasal fossae, and the floor of the orbit, and also enters into the 



THE MAXILLA 



101 



formation of two fossae, the zygomatic and sphenomaxillary, and two fissures, 
the sphenomaxillary and pterygomaxillary. The bone presents for examination 
a body and four processes — malar, nasal, alveolar, and palatal. 

The Body (corpus maxillae). — The body is somewhat cuboid and is hollowed 
out in its interior to form a large cavity, the antrum of Highmore {sinus maxillaris). 
Its surfaces are four — an external or facial, a posterior or zygomatic, a superior 
or orbital, and an internal or nasal. 

Surfaces. — The facial surface (fades anterior) (Fig. 70) is directed forward and 
outward. It presents at its lower part a series of eminences corresponding to the 
position of the anterior five teeth. Just above those for the incisor teeth is a 
depression, the incisive fossa, which gives origin to the Depressor alae nasi ; and 
below it to the alveolar border is attached a slip of the Orbicularis oris. Above 
and a little external to it the Compressor naris arises. More external is another 
depression, the canine fossa (fossa canina), larger and deeper than the incisive fossa, 
from which it is separated by a vertical ridge, the canine eminence, corresponding to 
the socket of the canine tooth. The canine fossa gives origin to the Levator anguli 
oris. Above the canine fossa is the infraorbital foramen {foramen infraorbiiale), 

Outer Surface. 



Incisive fossa. 




Posterior dental 
canals. 



Maxillary tuberosity. 



Fig. 70. — Left maxilla. Outer surface. 



the termination of the infraorbital canal; it transmits the infraorbital vessels and 
nerve. Sometimes the infraorbital canal opens by two, very rarely by three, 
orifices on the face. Above the infraorbital foramen is the margin of the orbit 
{margo infraorhitalis), which affords partial attachment to the Levator labii 
superioris. To the sharp margin of bone which bounds this surface in front 
and separates it from the internal surface is attached the Dilatator naris posterior. 
The posterior (fades infratem-poralis) or zygomatic surface is convex, directed 
backward and outward, and forms part of the zygomatic fossa. It is sepa- 
rated from the facial surface by a strong ridge of bone, the malar process, which 
extends upward from the socket of the second molar tooth. It presents about 
its centre several apertures leading to canals in the substance of the bone; 



102 SPECIAL ANATOMY OF THE SKELETON 

they are termed the posterior dental canals {foramina aheolaria), and transmit 
the posterior dental vessels and nerves. At the lower part of this surface is a 
rounded eminence, the maxillary tuberosity {tuber maxillare), especially prominent 
after the growth of the wisdom tooth, rough on its inner side for articulation with 
the tuberosity of the palate bone, and sometimes with the external pterygoid 
plate. It gives attachment to a few fibres of origin of the Internal pterygoid 
muscle. Immediately above this is a smooth surface, which forms the anterior 
boundary of the sphenomaxillary fossa; it presents a groove which, running ob- 
liquely downward, is converted into a canal by articulation with the palate bone, 
forming the posterior palatine or palatomaxillary canal for the descending palatine 
artery and great palatine nerve. The posterior border forms the anterior bound- 
ary of the pterygomaxillary fissure. 

The superior or orbital siu-face {fades orbitalis) is thin, smooth, triangular, 
and forms part of the floor of the orbit. It is bounded internally by an irregular 
margin, which in front presents a notch, the lacrimal notch {incisura lacrimalis), 
which receives the lacrimal bone; in the middle it articulates with the os planum of 
the ethmoid, and behind with the orbital process of the palate bone; bounded ex- 
ternally by a smooth, rounded edge which enters into the formation of the spheno- 
maxillary fissure, and which sometimes articulates at its anterior extremity with 
the orbital plate of the sphenoid; bounded in front by part of the circumference of 
the orbit, which is continuous on the inner side with the nasal, on the outer side 
with the malar process. Along the middle line of the orbital surface is a deep 
groove, the infraorbital groove {sidcus infraorbitalis) , for the passage of the infra- 
orbital vessels and nerve. The groove commences at the middle of the outer 
border of this surface, and, passing forward, terminates in a canal, which subdi- 
vides into two branches. One of the canals, the infraorbital canal, opens just below 
the margin of the orbit; the other, which is smaller, runs downward in the sub- 
stance of the anterior wall of the antrum; it is called the anterior dental canal, and 
transmits the anterior dental vessels and nerve to the front teeth of the maxilla. 
From the back part of the infraorbital canal a second small canal is sometimes 
given off, which runs downward in the outer wall of the antrum, and conveys the 
middle dental nerve to the biscupid teeth. Occasionally this canal is a branch of 
the anterior dental canal. 

At the inner and fore part of the orbital surface, just external to the lacrimal 
groove for the nasal duct, is a depression which gives origin to the Inferior oblique 
muscle of the eye. 

The internal surface (Fig. 71) is unequally divided into two parts by a horizontal 
projection of bone, the palatal process {processus palatinus); the portion above 
the palatal process is known as the nasal surface {fades nasalis). It forms part 
of the outer wall of the nasal fossa. Below the palate process is the cavity of 
the mouth. The superior division of the nasal surface presents a large, irregu- 
lar opening {hiatus maxillaris), leading into the maxillary sinus. At the upper 
border of this aperture are numerous broken cellular cavities, which in the articu- 
lated skull are closed by the ethmoid and lacrimal bones. Below the aperture 
is a smooth concavity which forms part of the inferior meatus of the nasal fossa, 
and behind it is a rough surface which articulates with the perpendicular plate of 
the palate bone, traversed by a groove which, commencing near the middle of the 
posterior border, runs obliquely downward and forward, and forms, when com- 
pleted by its articulation with the palate bone, the posterior palatine or palato- 
maxillary canal. In front of the opening of the antrum is a deep groove, con- 
verted into a canal {canalis nasolacrimalis) by the lacrimal and turbinated bones. 
The groove is called the lacrimal groove {sulcus lacrimalis), and lodges the nasal 
duct. More anteriorly is a well-marked rough ridge, the inferior turbinated crest 
{crista conchalis), for articulation with the turbinated bone. The shallow con- 



THE MAXILLJE 



103 



cavity above this ridge forms part of the middle meatus of the nose, while that 
below it forms part of the inferior meatus. The portion of this surface below 
the palatal process is concave, rough, and uneven, and perforated by numerous 
small foramina for the passage of nutrient vessels. It enters into the formation 
of the roof of the mouth. 

The antrum of Highmore (sinus maxillaris) is a pyramidal cavity hollowed 
out of the body of the maxilla. It varies much in size. It is in most cases a 
large cavity, but in some is very small. The apex of the antrum, directed outward, 
is formed by the malar process ; its base by the outer wall of the nose. Its walls 
are everywhere exceedingly thin, and correspond to the orbital, facial, and zygo- 
matic surfaces of the body of the bone. The floor is formed by the alveolar process 
of the maxilla. The roof corresponds to the orbital plate. Its inner wall, or base, 
presents, in the disarticulated bone, a large, irregular aperture (hiatus maxil- 
laris), which communicates with the nasal fossa. The margins of this aperture 
are thin and ragged, and the aperture itself in the articulated skull is much con- 



■^jSi-/''-o^ 



£on^ partially closinff orifice of antrum 
marked in outline 



Ethmoid. 

Turbinated. 

Palate. 



Anterior nasal spine. 



Bristle passed 
through anterior 
palatine candl. 




^"-^W^iwV^. 



Fig. 71. — Left maxilla. Internal surface. 

tracted by its articulation with the ethmoid above, the turbinated bone below, 
and the palate bone behind.^ In the articulated skull this cavity communicates 
with the middle meatus of the nasal cavity, generally by two small apertures 
left between the above-mentioned bones. In the recent state usually only one 
small opening exists, near the upper part of the cavity, sufficiently large to 
admit the end of a probe, the other being closed by the lining membrane of 
the sinus. 

Crossing the cavity of the antrum are often seen several projecting laminse of 
bone, similar to those seen in the sinuses of the cranium; on its posterior wall are 
the posterior dental canals, transmitting the posterior dental vessels and nerves to 
the teeth. Projecting into the floor are several conical processes, corresponding 



' In some cases, at any rate, the lacrimal bone encroacfies 'slightly on the anterior superior portion of the 
opening, and assists in forming the inner wall of the antrum. 



104 SPECIAL ANA TOMY OF THE SKELETON 

to the roots of the first and second molar teeth; in some cases the floor is per- 
forated by the teeth in this situation; projecting into the antrum from the roof 
is a ridge corresponding to the infraorbital canal. 

The Processes. — The malar process (^processus zygomaticus) is a rough, trian- 
gular eminence, situated at the angle of separation of the facial from the zygo- 
matic surface. In front it is concave, forming part of the facial surface; behind it 
is also concave, and forms part of the zygomatic fossa; above it is rough and 
serrated for articulation with the malar bone; while below a prominent ridge 
marks the division between the facial and zygomatic surfaces. A small part of 
the Masseter muscle arises from this process. 

The nasal process (processus frontalis) is a strong, triangular plate of bone, which 
projects upward, inward, and backward by the side of the nose, forming part 
of its lateral boundary. Its external surface is concave, smooth, perforated by 
numerous foramina, andgivesattachment totheLevatorlabiisuperiorisalaecjue nasi, 
the Orbicularis palpebrarum, and the Tendo oculi. Its infernal surface forms part 
of the outer wall of the nasal fossa; at its upper part it presents a rough, uneven 
surface, which articulates with the ethmoid bone, closing in the anterior ethmoidal 
cells; below this is a transverse ridge, the superior turbinated crest (crista ethmoi- 
dalis), for articulation with the middle turbinated process of the ethmoid; below 
the crest is a shallow, smooth concavity which forms part of the middle meatus; 
below this again is the inferior turbinated crest (already described), where the pro- 
cess joins the body of the bone. Its upper border articulates with the nasal notch 
of the frontal bone. The anterior border of the nasal process is thin, directed 
obliquely downward and forward, and presents a serrated edge for articulation with 
the nasal bone; its posterior border is thick, and hollowed into a groove, the lacrimal 
groove, for the nasal duct; of the two margins of this groove, the inner one articu- 
lates with the lacrimal bone, the outer one forms part of the circumference of the 
orbit. Just where the latter joins the orbital surface is a small tubercle, the 
lacrimal tubercle, which articulates with the hamular process of the lacrimal bone. 
The lacrimal groove in the articulated skull is converted into a canal {canalis 
lacrimalis) by the lacrimal bone and lacrimal process of the turbinated bene; it 
is directed downward, and a little backward and outward, is about the diameter 
of a goose-quill, slightly narrower in the middle than at either extremity, and 
terminates below in the inferior meatus. It lodges the nasal duct. 

The alveolar process (^processus alveolaris) is the thickest and most spongy 
part of the bone, broader behind than in front, and excavated into deep cavities 
for the reception of the teeth (alveoli dentales). These cavities are eight in number, 
and vary in size and depth according to the teeth they contain. That for the 
canine tooth is the deepest; those for the molars are the widest, and subdivided 
into minor cavities by septa; those for the incisors are single, but deep and narrow. 
The Buccinator muscle arises from the outer surface of this process as far forward 
as the first molar tooth. After the loss of the prominent teeth at any time, but 
especially in old age, this process, like that of the mandible, is absorbed. 

The palatal process (processus palatinus), thick and strong, projects horizon- 
tally inward from the inner surface of the body. It is much thicker in front than 
behind, and forms a considerable part of the floor of the nostril and the roof of 
the mouth. Its inferior surface (Fig. 72) is concave, rough and uneven, contains 
numerous little cavities for the glands of the mucous membrane, and forms part 
of the roof of the mouth. This surface is perforated by numerous foramina for 
the passage of the nutrient vessels, channelled at the back part of its alveolar border 
by a longitudinal groove, sometimes a canal, for the transmission of the posterior 
palatine vessels, and the great posterior palatine ner^'e from Meckel's ganglion, 
and presents little depressions for the lodgement of the palatine glands. When 
the two maxillae are articulated, a large fossa may be seen in the middle 



THE MAXILLJE 



105 



Anterior palatine canat. 



Foramina ofStens 



^^-^^Fo) amen of Scarpa, 



Palate proceis uj 

maxilla K^ V 

1 /- 



line, immediately behind the incisor teeth. This is the anterior palatine fossa. 
On examining the bottom of this fossa four canals are seen: two branch off 
laterally to the right and left nasal fossae, and two — one in front and one behind 
— lie in the middle line. Tlie former pair of these openings are named the 
incisor foramina, or foramina of Stenson; they are the openings of the forking incisor 
canal, through which pass the anterior or terminal branches of the descending 
or posterior palatine arteries, which ascend from the mouth to the nasal fossa?, 
and they contain the remains of Jacobson's organ. The canals in the middle line 
are termed the foramina 
of Scarpa, and transmit 
the nasopalatine nerves, 
the left passing through 
the anterior, and the right 
through the posterior, 
canal. Occasionally in 
adults' skulls, often in 
children's skulls, on the 
palatal surface of the 
process a delicate linear 
suture may sometimes be 
seen extending from the 
anterior palatine fossa to 
the interval between the 
lateral incisor and the 
canine tooth. This marks 
out the premaxillary bones 
(o.s incisivwn) on each 
side, and includes the 
whole thickness of the 
alveolus, the correspond- 
ing part of the floor of 
the nose, and the anterior 
nasal spine, and contains 
the sockets of the incisor teeth; in some animals it exists as a separate bone. The 
upper surface of the palatal process is concave from side to side, smooth, and 
forms part of the floor of the nose. It presents the upper orifices of the foramina 
of Stenson and Scarpa, the former being on each side of the middle line, the 
latter being situated in the intermaxillary suture, and therefore not visible unless 
the two bones are placed in apposition. The otder border of the palatal process 
is incorporated with the rest of the bone. The inner border is thicker in front 
than behind, and is raised above into a ridge, the nasal crest {crista uasalis), 
which, with the corresponding ridge in the opposite bone, forms a groove for 
the reception of the vomer. In front this crest rises to a considerable height, and 
this portion is named the incisor crest. The anterior margin is bounded by the 
thin, concave border of the opening of the nose, prolonged forward internally into 
a sharp process, forming, with a similar process of the opposite bone, the anterior 
nasal spine {spina nasalis anterior). The posterior border is serrated for articu- 
lation with the horizontal plate of the palate bone. 




palatine canals. 



Accessory palatine foramina. 

Fig. 72. — The palate and alveolar arch. 



Development.— This bone commences to ossify at a very early period, and ossification 
proceeds in it with great rapidity, so that it is difficult to ascertain with certainty ks precise 
number of centres. It appears, however, ]:)robable that it is ossified from six centres, 
which develop in membrane: (1) One, the ocit/oHn.raZ, which forms that portion of the body 
of the bone which lies internal to the infraorbital canal, including the floor of the orbit, the 
outer wall of the nasal fossa, and the nasal process. (2) A malar, which gives origin to that 



106 



SPECIAL ANATOMY OF THE SKELETON 




Anterior Surjace. 



portion of the bone which has external to the infraorbital canal and the malar process. (3) 
A palatal, from which is developed the palatal process posterior to Stenson's canal and the 
adjoining part of the nasal wall. 4. A premaxiUary, for the front part of the alveolus, which carries 
the incisor teeth and corresponds to the premaxillary bone of the lower animals. (5) A nasal, 
that gives rise to the nasal process and the portion above the canine tooth. (6) An infravomerine, 
that lies beneath the vomer and between the palatal and premaxillary centres. The premaxillary 
centre is in close association with the development of the perpendicular plate of the ethmoid and 
the vomer. According to Albrecht it develops from two centres of ossification, each having an 
incisive tooth. The one possessing the mesal segment he calls the 
endogiiatldon. The lateral segment he calls the mesognathion, 
while to the maxilla he gives the name exognathion. These seg- 
ments are separated by five sutures. The failure of union of any 
of these segments will lead to the various forms of cleft palate. 
These centres appear about the eighth week, and by the tenth 
week have become fused together so that the bone consists of two 
portions, one the maxilla proper, and the other the premaxillary 
portion. The suture between these two portions on the palate 
persists until middle life, but is not to be seen on the facial surface. 
This is believed by Callender to be due to the fact that the front 
wall of the sockets of the incisive teeth is not formed by the pre- 
maxillary bone, but by an outgrowth from the facial part of the 
maxilla. The antrum appears as a shallow groove on the inner 
surface of the bone at an earlier period than any of the other nasal 
sinuses, its development commencing about the fourth month of 
fetal life, and reaches its full size after the second dentition. The 
sockets for the teeth are formed by the growing downward of 
two plates from the dental groove, which subsequently becomes 
divided by partitions jutting across from the one to the other. If 
the two palatal processes fail to unite partially or completely, a 
partial or complete cleft palate results. 

Articulations. — With nine bones, two of the cerebral cranium, 
the frontal and ethmoid, and seven of the face — viz., the nasal, 
malar, lacrimal, turbinated, palate, vomer, and its fellow of the 
opposite side. Sometimes it articulates with the orbital plate of 
the sphenoid, and sometimes with its external pterygoid plate. 
Attachment of Muscles. — To twelve — the Orbicularis palpebrarum, Obliquus oculi infe- 
rior, Levator labii superioris alaeque nasi. Levator labii superioris, Levator anguli oris, Com- 
pressor naris. Depressor alae nasi. Dilatator naris posterior, Masseter, Buccinator, Internal 
pterygoid, and Orbicularis oris. 

Applied Anatomy. — It is from the extreme thinness of the walls of the antrum that we are 
enabled to explain how a tumor growing from the antrum encroaches upon the adjacent parts, 
pushing up the floor of the orbit and displacing the eyeball, projecting inward into the nose, 
protruding forward on to the cheek, and making its way backward into the zygomatic fossa 
and downward into the mouth. 




Inferior Surface. 



CHANGES PRODUCED IN THE UPPER JAW BY AGE. 

At birth and during infancy the diameter of the bone is greater in an antero-posterior than 
in a vertical direction. Its nasal process is long, its orbital surface large, and its tuberosity 
well marked. In the adult the vertical diameter is the greater, owing to the development of 
the alveolar process and the increase in size of the antrum. In old age the bone approaches 
again in character to the infantile condition; its height is diminished, and after the loss of the 
teeth the alveolar process is absorbed, and the lower part of the bone contracted and diminished 
in thickness. 



The Lacrimal Bone (Os Lacrimale). 



The lacrimal (lacrima, a, tear) is the smallest and most fragile bone of the face. 
There are two lacrimal bones. They are situated at the front part of the inner 
wall of the orbit (Fig. 67), and resemble somewhat in form, thinness, and size a 
finger nail ; hence, they are termed the ossa un^is. Each bone presents for exami- 
nation two surfaces and four borders. 




THE MALAB BONE ' 107 

Surfaces. — The external or orbital surface (Fig. 74) is divided by a vertical 
ridge, the lacrimal crest {crista lacrimalis posterior), into two parts. The portion 
of bone in front of this ridge presents a smooth, concave, longitudinal groove 
(sulcus lacrimalis), the free margin of which unites with the nasal process of the 
maxilla, completing the lacrimal canal. The upper part of this groove {fossa 
sacci lacrimalis) lodges the lacrimal sac; the lower part lodges the nasal duct. 
The portion of bone behind the ridge is smooth, slightly concave, and forms 
part of the inner wall of the orbit. The ridge, with a part of the orbital surface 
immediately behind it, affords origin to the Tensor tarsi 
muscle ; it terminates below in a small hook-like projection, wuhfrmtai. 

the hamular process {hamulus lacrimalis), which articulates 
with the lacrimal tubercle of the maxilla and completes the 
upper orifice of the lacrimal canal. It sometimes exists as a 
separate piece, which is then called the lesser lacrimal bone. 

The internal or nasal surface presents a depressed furrow, 
corresponding to the ridge on its outer surface. The sur- 
face of bone in front of this forms part of the middle 
meatus, and that behind it articulates with the ethmoid 
bone, closing in the anterior ethmoidal cells. 

Borders. — Of the four borders, the anterior is the long- 
est, and articulates with the nasal process of the maxilla. ,^ fig. 74,— Left lacrimal 

f^^, , . , . , -11 bone. iivXternal surface. 

ihe postenor, thm and uneven, articulates with the os (Siightiy enlarged.) 
planum of the ethmoid. The superior, the shortest and 
thickest, articulates with the internal angular process of the frontal bone. The 
inferior is divided by the lower edge of the vertical crest into two parts; the 
posterior part articulates with the orbital plate of the maxilla; the anterior 
portion is prolonged downward into a pointed process, which articulates with 
the lacrimal process of the turbinated bone and assists in the formation of the 
lacrimal canal. 

Development. — From a single centre, which makes its appearance in membrane at about 
the eighth or ninth week. 

Articulations. — With four bones — two of the cerebral cranium, the frontal and ethmoid, 
and two of the face, the maxilla and the turbinated. 

Attachment of Muscles. — To one muscle, the Tensor tarsi. 



The Malar Bone (Os Zygomaticum). 

The malar bone is a quadrangular bone, situated at the upper and outer part of 
the face. It forms the prominence of the cheek, part of the outer wall and floor 
of the orbit, and part of the temporal and zygomatic fossae (Fig. 7.5). Each bone 
presents for examination an external and an internal surface; three processes, the 
frontal, orbital, and zygomatic processes; and four borders. 

Surfaces.— The external surface {fades malaris) (Fig. 76) is smooth, convex, 
perforated near its centre by a small aperture, the malar foramen, for the passage 
of nerves and vessels from the orbit. The malar surface is co-\-ered by the Orbicu- 
laris palpebrarum muscle, and affords attachment to the Zygomaticus major and 
minor muscles. 

The internal surface {fades temporalis) (Fig. 77), directed backward and inward, 
is conca-\'e, presenting anteriorly a rough, triangular surface, for articulation with 
the maxilla ; and behind, a smooth concave surface, which above forms the anterior 
boundary of the temporal fossa, and below, where it is wider, forms part of the 
zygomatic fossa. This surface presents, a little above its centre, the aperture of 



108 



SPECIAL ANATOMY OF THE SKELETON 



a malar canal {foramen zygomaticotemporale) , and affords attachment at its 
lower part to a portion of the Masseter muscle. 

Processes. — ^The frontal process (^processus frontosphenoidalis) is thick and 
serrated, and articulates with the external angular process of the frontal bone. To 
its orbital margin is attached the external tarsal ligament. 



Frontal pi Oct s'i Ert angular pi ocess 




Ki^ht inilir bone m s%tu 



The orbital process is a thick and strong plate, which projects backward from the 
orbital margin of the bone. Its supero-infernal surface (fades orbitalis), smooth 
and concave, forms, by its junction with the orbital surface of the maxilla and with 
the greater wing of the sphenoid, part of the floor and outer wall of the orbit. Its 
temporal surface, smooth and concave, forms part of the zygomatic and temporal 



yfiih froittal. 



Si-istl^s passed / 
through iempoi o- ^ e 
malar canals. , ^ &.) 




fossfe. Its anterior viargin is smooth and rounded, forming part of the circum- 
ference of the orbit. Its superior margin, rough and directed horizontally, artic- 
ulates with the frontal bone behind the external angular process. Its posterior 



THE PALATE BONE 109 

inargin is rough and serrated for articulation with the sphenoid ; wtpniaUy it is 
also serrated for articulation with the orbital surface of the maxilla. At the 
angle of junction of the sphenoidal and maxillary portions a short, rounded, non- 
articular margin is generally seen; this forms the anterior boundary of the spheno- 
maxillary fissure; occasionally no such nonarticular margin exists, the fissure 
being completed by the direct junction of the maxilla and sphenoid bones or by 
the interposition of a small Wormian bone in the angular interval between them. 
On the supero-internal surface of the orbital process is seen the orifice of one of the 
temporomalar canals. This canal may be bifurcated, or there may be two canals 
from the beginning; one of these usually opens on the temporal surface, the 
other (occasionally two) on the facial surface; they transmit filaments of the 
orbital branch of the superior maxillary nerve. 

The zygomatic process {processus temporalis), long, narrow, and serrated, articu- 
lates with the zygomatic process of the temporal bone. 

Borders. — The antero-superior {orbital border) is smooth, arched, and forms 
a considerable part of the circumference of the orbit. The antero-inferior (maxil- 
lary border) is rough, and bevelled at the expense of its inner table, to articulate 
with the maxilla, affording attachment by its margin to the Levator labii superioris, 
just at its point of junction with the maxilla. The postero-superior (temporal 
border) curved like an italic letter/, is continuous above, with the commencement 
of the temporal ridge; below, with the upper border of the zygomatic arch; it 
affords attachment to the temporal fascia. The postero-inferior (masseteric 
border) is continuous with the lower border of the zygomatic arch, affording 
attachment by its rough edge to the Masseter muscle. 

Development. — The malar bone ossifies generally from three centres, which appear about the 
eighth week — one for the zygomatic and two for the orbital portion — and which fuse about the 
fifth month of fetal life. The bone is sometimes, after birth, seen to be divided by a horizontal 
suture into an upper and larger and a lower and smaller division. In some primates the malar 
bone consists of two parts, an orbital and a malar. 

Articulations. — With four bones — three of the cranium, frontal, sphenoid, and temporal; and 
one of the face, the maxilla. 

Attachment of Muscles. — To four — the Levator labii superioris proprius, Zygomaticus 
major and minor, and Masseter. 



The Palate Bone (Os Palatinum). 

The palatal bones' are situated at the back part of the nasal fossre ; they are wedged 
in between the maxilla and the pterygoid processes of the sphenoid (Fig. 78). 
Each bone assists in the formation of three cavities — the floor and outer wall of the 
nose, the roof of the mouth, and the floor of the orbit — and enters into the formation 
of two fossae, the sphenomaxillary and pterygoid fossae; and one fissure, the sphe- 
nomaxillary fissure. In form the palate bone somewhat resembles the letter L, 
and may be divided into an inferior or horizontal plate and a superior or vertical 
plate. 

The Horizontal Plate (pars liorizontaUs) (Figs. 79 and 80) is of a quadrilateral 
form, and presents two surfaces and four borders. 

Surfaces. — The superior or nasal surface (fades nasalis^, concave from side to 
side, forms the back part of the floor of the nasal cavity. 

The inferior or palatine surface (fades palatina), slightly concave and rough, forms 
the back part of the hard palate. At its posterior part may be seen a transverse 
ridge, more or less marked, for the attachment of part of the aponeurosis of the 

' The word palate is frequently \ised as an adjective. Palatal is the correct form (froni palatum, the palate), 
but usage sanctions palatine in certain compounds, despite the fact that palatine is derived from palatium, ix 
palace. This is another example of what is charitably called a "late Latin" form, akin to hallux and hallucis. 
— [Editor.] 



110 



SPECIAL ANATOMY OF THE SKELETON 



Tensor palati muscle. At the outer extremity of this ridge is a deep groove, the 
pterygopalatine groove (sulcus pterygopalatinus) , converted into a canal by its 
articulation with the tuberosity of the maxilla, and forming the lower end of the 
posterior palatine canal {canalis ijterycjojjalatiniis) . Near this groove the orifices 
of one or two small canals, accessory posterior palatine canals (canales iKilatim), 
may be seen for the passage of the middle and posterior palatine nerves from the 
sphenopalatine (Meckel's) ganglion. Through the posterior palatine canal 
emerge the descending palatine artery and the great posterior palatine nerve. 

Borders. — ^The anterior is serrated, bevelled at the expense of its inferior sur- 
face, and articulates with the palatal process of the maxilla. The posterior 
is concave, free, and serves for the attachment of the soft palate. Its inner 
extremity is sharp and pointed, and when united with the opposite bone forms a 



Sphenopalatine notch. 



Sup. turbinated crest, n^? 

N-, MIDQ 



Inf. turbinated crest. 




Sup turbinated crest. 



Inf turbinated crest. 



Ant. nasal spiiie. 



projecting process, the palatine spine (.'.■piua nasalis fostcrior), for the attachment 
of the Azygos uvulae muscle. The external is united with the lower part of the 
perpendicular plate almost at right angles. The internal, the thickest, is serrated 
for articulation with its fellow of the opposite side; its superior edge is raised into 
a ridge, which, united with the opposite bone, forms a crest (crista nasalis), into 
which the vomer is received. 

The Vertical or Perpendicular Plate (pars perpend icidaris) (Figs. 79 and 80) 
forms the back part of the outer wall of the nasal fossa, is thin, of an oblong form, 
and directed upward and a little inward. It presents two surfaces, an external 
and an internal, and three borders. 

Surfaces. — The internal, medial, or nasal surface (fades nascdis) presents at its 
lower part a broad, shallow depression, which forms part of the inferior meatus 
of the nose. Immediately above this is a well-marked ridge, the inferior turbin- 
ated crest (crista conchali.s), for articulation with the turbinated bone; above this 
a second broad, shallow depression, which forms part of the middle meatus, sur- 
mounted above by a horizontal ridge less prominent than the inferior, the superior 
turbinated crest (crista ethmoidalis) , for articulation with the middle turbinated 



THE PALATE BONE 



111 



process. Above the superior turbinated crest is a narrow, horizontal groove, 
which forms part of the superior meatus. 

The external or lateral surface (J'aclesmaxillaris) is rough and irregular throughout 
the greater part of its extent, for articulation with the inner surface of the maxilla, 
its upper and back part being smooth where it enters into the formation of the 
sphenomaxillary fossa; it is also smooth in front, where it covers the orifice of the 
antrum. Toward the back 

Orbital process. 

Orbilal surface. 



Superior meatus 
Sphenopalatine /c 




Maxillary surface. 



Maxillary 
* process. 



Fig. 79. 



Horizontal Plate. 

-Left palate bone. Internal 



(Enlarged.) 



part of this surface is a deep 
groove, the pterygopalatine 
groove, converted into a canal, 
the posterior palatine canal, 
by its articulation with the 
maxilla. It transmits the 
posterior or descending pala- 
tine vessels and the great or 
anterior palatine nerve from 
Meckel's ganglion. 

Borders. ■ — The anterior 
border (Fig. 79) is thin, irreg- 
ular, and presents opposite 
the inferior turbinated crest 
a pointed, projecting lamina, 
the maxillary process (processiis 
maxillaris), which is directed 
forward, and closes in the 
lower and back part of the 
opening of the antrum. 

The posterior border (Fig. 80) presents a deep groove, the edges of which are 
serrated for articulation with the pterygoid process of the sphenoid. At the 
lower part of this border is seen a pyramidal process of bone, the tuberosity of the 
palate {processus pyramidalis), which is received into the angular interval between 

the two pterygoid plates of the sphenoid 
at their inferior extremity. This process 
presents at its back part a median groove 
and two lateral surfaces. The groove is 
smooth, and forms part of the pterygoid 
fossa, affording attachment to the Internal 
pterygoid muscle; while the lateral surfaces 
are rough and uneven, for articulation 
with the anterior border of each pterygoid 
plate. A few fibres of the Superior con- 
strictor of the pharynx arise from the 
tuberosity of the palate bone. The base 
of this process, continuous with the hori- 
zontal portion of the bone, presents the 
apertures of the accessory posterior pala- 
tine canals, through which pass the two 
smaller descending branches of Meckel's 
ganglion; while its outer surface is rough 
for articulation with the inner surface of 
the body of the maxilla. 

The superior border of the vertical plate 
presents two well-marked processes separated by an intervening notch. The ante- 
rior, or larger, is called the orbital pi-ocess ; the posterior, the sphenoidal process. 



Orbital process. 

^^^^^sw tcce 



^Sphenopalatine 
foramen, 

, Sphenoidal process. 
~ Articular portion. 
J^on-artictdar portion. 




Fig. 80. — Left palate bone. Posterior 
(Enlarged.) 



112 SPECIAL ANATOMY OF THE SKELETON 

Processes. — The orbital process {processus orhitalis) , directed upward and out- 
ward, is placed on a higher level than the sphenoidal. It presents five surfaces, 
which enclose a hollow cellular cavity, and is connected with the perpendicular 
plate by a narrow, constricted neck. Of these five surfaces, three are articular, 
two nonarticular or free surfaces. The three articular are the anterior or maxillary 
surface, which is directed forward, outward, and downward, is of an oblong forni, 
and rough for articulation with the maxilla. The posterior or sphenoidal surface is 
directed backward, upward, and inward. It ordinarily presents a small, open cell, 
the orbital sinus, which communicates with the sphenoidal cells, and the mar- 
gins of which are serrated for articulation with the vertical part of the sphe- 
noidal turbinated process. The internal or ethmoidal surface is directed inward, 
upward, and forward, and articulates with the lateral mass of the ethmoid bone. 
In some cases the cellular cavity opens on the internal surface of the bone ; it then 
communicates with the posterior ethmoidal cells. More rarely it opens on both 
surfaces, and then communicates with both the posterior ethmoidal and the 
sphenoidal cells. The nonarticular or free surfaces are the superior or orbital 
surface, directed upward and outward, of triangular form, concave, smooth, and 
forming the back part of the floor of the orbit; and the external or zygomatic 
surface, directed outward, backward, and downward, of an oblong form, smooth, 
lying in the sphenomaxillary fossa, and looking into the zygomatic fossa. The 
latter surface is separated from the orbital by a smooth, rounded border, which 
enters into the formation of the sphenomaxillary fissure. 

The sphenoidal process (processus sphenoidalis) of the palate bone is a thin, com- 
pressed plate, much smaller than the orbital, and directed upward and inward. 
It presents three surfaces and two borders. The superior surface, the smallest 
of the three, articulates with the under surface of the sphenoidal turbinated pro- 
cess; it presents a groove, which contributes to the formation of the pterygopala- 
tine canal. The internal surface is concave, and forms part of the outer wall of 
the nasal fossa. The external surface is divided into an articular and a nonartic- 
ular portion; the former is rough, for articulation with the inner surface of the 
internal pterygoid plate of the sphenoid; the latter is smooth, and forms part of 
the sphenomaxillary fossa. The anterior border forms the posterior boundary of 
the sphenopalatine notch. The posterior border, serrated at the expense of the 
outer table, articulates with the inner surface of the internal pterygoid plate. 

The orbital and sphenoidal processes are separated from each other by a deep 
notch, the sphenopalatine notch ( incisura sphenopalatina), which is converted into 
a foramen, the sphenopalatine foramen (foramen sphenopalatinum) , by articulation 
with the under surface of the body of the sphenoid bone. Sometimes the two pro- 
cesses are united above, and form between them a complete foramen (Figs. 79 
and 80), or the notch is crossed by one or more spiculse of bone, so as to form 
two or more foramina. In the articulated skull this foramen is seen to pass from 
the sphenomaxillary fossa into the back part of the superior meatus. It trans- 
mits the sphenopalatine vessels and the superior nasal and nasopalatine nerves. 

Development. — From a single centre, which makes its appearance in membrane about the 
second month at the angle of junction of the two plates of the bone. From this point ossification 
spreads inward to the horizontal plate, downward into the tuberosity, and upward into the vertical 
plate. In the fetus the horizontal plate is much larger than the vertical, and even after it is 
fully ossified the whole bone is remarkable for its shortness. 

Articulations. — With six bones — the sphenoid, ethmoid, maxilla, turbinated, vomer, and 
opposite palate. 

Attachment of Muscles. — To four — the Tensor palati, Azygos uvulae, Internal pterygoid, 
and Superior constrictor of the pharynx. 



THE TURBINATED BONE 



\VA 



The Turbinated Bone (Concha Nasalis Inferior), 

The turbinated bones are situated one on each side of the outer wall of each 
nasal fossa. Each consists of a layer of thin, spongy bone, curled upon itself like a 
scroll — hence its name "turbinated" — and extends horizontally along the outer 
wall of the nasal fossa, immediately below the orifice of the antrum (Fig. SI). 
Each bone presents two surfaces, two borders, and two extremities. 




Fig. 81.~N;isal cavity, right lateral wall, from the left. (Spalteholz.) 



Surfaces. — ^The internal surface (Fig. 82) is convex, perforated by numerous 
apertures, and traversed by longitudinal grooves and canals for the lodgement 
of arteries and veins. In the recent state it is covered by the lining membrane of 
the nose. The external surface is concave (Fig. 83), and forms part of the inferior 
meatus. 




-Right turbinated bo 



Internal surface. Fic. S3. — Right turbinated bone. External surface. 



Borders. — Its upper border is thin, irregular, and connected to various bones 
along the outer wall of the nose. It may be divided into three portions; of these, 
tlie anterior articulates with the inferior turbinated crest of the maxilla ; the poste- 
rior with the inferior turbinated crest of the palate bone; the middle portion of the 



114 SPECIAL ANATOMY OF THE SKELETON 

superior border presents three well-marked processes, which vary much in their 
size and form. Of these, the anterior and smallest is situated at the junction of 
the anterior fourth with the posterior three-fourths of the bone; it is small and 
pointed, and is called the lacrimal process {-processus lacrimal is); it articulates by 
its apex with the anterior inferior angle of the lacrimal bone, and by its margins 
with the groove on the back of the nasal process of the maxilla, and thus assists 
in forming the canal for the nasal duct. At the junction of the two middle fourths 
of the bone, but encroaching on its posterior fourth, a broad, thin plate, the eth- 
moidal process (processus ethmoidalis), ascends to join the unciform process of the 
ethmoid; from the lower border of this process a thin lamina of bone curves down- 
ward and outward, hooking over the lower edge of the orifice of the antrum, which 
it narrows below; it is called the maxillary process (processus maxillaris), and fixes 
the bone firmly to the outer wall of the nasal fossa. The inferior border is free and 
thick, more especially in the middle of the bone. Both extremities are more or 
less narrow and pointed, the posterior being the more tapering. If the bone is 
held so that its outer concave surface is directed backward (i. e., toward the holder), 
and its superior border, from which the lacrimal and ethmoidal processes project, 
upward, the lacrimal process will be directed to the side to which the bone belongs.' 

Development. — From a mngle centre, which makes its appearance about the middle of fetal 
life in the outer wall of the cartilaginous nasal septum. 

Articulations. — With four bones — one of the cerebral cranium, the ethmoid, and three of 
the face, the maxilla, lacrimal, and palate. 

No muscles are attached to this bone. 



The Vomer. 

The vomer is a single bone, situated vertically at the back part of the nasal 
fossae, forming part of the septum of the nose (Fig 84). It is thin, somewhat like a 
ploughshare in form; but varies in different individuals, being frequently bent to 
one or the other side ; it presents for examination two surfaces and four borders. 

Surfaces. — ^The lateral surfaces are smooth, marked by small furrows for the 
lodgement of bloodvessels, and by a groove on each side, sometimes a canal, 
the nasopalatine groove, or canal, which runs obliquely downward and forward to 
the intermaxillary suture; it transmits the nasopalatine nerve. 

Borders. — ^The superior border, the thickest, presents a deep groove, bounded 
on each side by a horizontal projecting leaf of bone; these leaves are the alse (alae 
vomeris). The groove formed by the alae receives the rostrum of the sphenoid, 
while the alse are overlapped and retained by the vaginal processes, which pro- 
ject on the under surface of the body of the sphenoid at the base of the pterygoid 
processes. At the front of the groove a fissure is left for the transmission of blood- 
vessels to the substance of the bone. The inferior border, the longest, is broad and 
uneven in front, where it articulates with the crests of the two maxillae ; thin and 
sharp behind, where it joins with the palate bones. The upper half of the anterior 
border usually consists of two laminse of bone, in the groove between which is 
received the perpendicular plate of the ethmoid ; the lower half, also separated into 
two lamellse, receives between them the lower margin of the septal cartilage of the 
nose. The posterior border is free, concave, and separates the nasal fossee behind. 
It is thick and bifid above, thin below. 

The surfaces of the vomer are covered by mucous membrane, which is inti- 
mately connected with the periosteum, with the intervention of very little, if any, 
submucous connective tissue. 

1 If the lacrimal process is broken off, as is often the case, the side to which the bone belongs may be known 
by recollecting that the maxillary process is nearer the back than the front of the bone. 



THE MANDIBLE, OR LOWER JAW 



115 




Space for fnavqida) 
cartilage of septum '*^^^PI||| 



Lo'.ti urn of sphenoid. 



Fig. S4. — Vomer ; 

Development.— The vomer at an 
early period consists of two laminse, 
separated by a very considerable in- 
terval, and enclosing between them a 
plate of cartilage, the vomerine car- 
tilage, which is prolonged forward 
to form the remainder of the septum. 
Ossification commences, about the 
eighth week, in the membrane at the 
postero-inferior part of this cartilage 
from two centres, one on each side of 
the middle line, which extend to form 
the two laminse. The intervening 
cartilaginous plate is absorbed. They 
begin to coalesce at the lower part, 
but their union is not complete until 
after puberty. 

Articulations. — With nx bones — two of the cerebral cranium, the sphenoid and ethmoid, 
and four of the face, the maxillse and the two palate bones; and with the cartilage of the septum. 

The vomer has no muscles attached to it. 




With maxillae and palate. 

Fig. 85, — The vomer. 



The Mandible, or Lower Jaw (Mandibula). 



The mandible, the largest and strongest bone of the face, serves for the reception 
of the lower teeth. It consists of a curved, horizontal portion, the body, and two 
perpendicular portions, the rami, which join the back part of the body nearly at 
right angles. 

The Body (corpus mandibulae) (Fig. 86). — The body is convex in its general 
outline, and curved somewhat like a horseshoe. It presents for examination 
two surfaces and two borders. , 

Surfaces. — ^The external surface is convex from side to side, concave from above 
downward. In the median line is a vertical ridge, the symphysis, which extends 



116 



SPECIAL ANATOMY OF THE SKELETON 



from the upper to the lower border of the bone, and indicates the point of junction 
of the two pieces of which the bone is composed at an early period of life. The 
lower part of the ridge terminates in a prominent triangular eminence, the mental 
process (protuberantia mentalis). This eminence is rounded below, and often 



Coronoid process. 



Condyle 




Groove for faaal aitery 
-The mandible. Outer surface. 



presents a median depression separating two processes, the mental tubercles (iubercula 
mentalia). It forms the chin, a feature peculiar to the human skull. On either 
side of the symphysis, just below the cavities for the incisor teeth, is a depression, 
the incisor fossa, for the attachment of the Levator menti; more externally is 



> ^''". 




Fig. 87. — The mandible. Inner surface. Side view. 



attached a portion of the Orbicularis oris, and still more externally, a foramen, 
the mental foramen (foramen meiitale), for the pas'sage of the mental vessels and 
nerve. This foramen is placed just below the interval between the two bicuspid 
teeth. Running outward from the base of the mental process on each side is a 



THE MANDIBLE, OB LOWER JAW II7 

ridge, the external oblique line (linea obliqua). The ridge is at first nearly hori- 
zontal, but afterward inclines upward and backward, and is continuous with the 
anterior border of tire ramus; it aii'ords attachment to the Depressor labii inferioris 
and Depressor anguH oris; below it the Platysma is attached. 

The Internal surface (Fig. 87) is concave from side to side, convex from above 
downward. In the middle line is an indistinct linear depression, corresponding 
to the symphysis externally; on either side of this depression, just below its 
centre, are two prominent tubercles, one above and one below, the genial 
tubercles {spinae mentales) , which afford attachment, the upper pair to the Genio- 
hyoglossi, the lower pair to the Geniohyoidei, muscles. Sometimes the tubercles 
on each side are blended into one; at others they all unite into an irregular 
eminence; or, again, nothing but an irregularity may be seen on the surface of 
the bone at this part. On either side of the genial tubercles is an oval depression, 
the sublingual fossa (fovea sublingualis), for the lodgement of the sublingual gland; 
and beneath the fossa a rough depression, tlie digastric fossa (fossa digastrica), on 
each side, wliich gives attachment to the anterior belly of the Digastric muscle. 

At the back part of the sublingual fossa the internal oblique line, or mylohyoid 
ridge (linea mylohyoidea), commences; it is at first faintly marked, but becomes 
more distinct as it passes upward and outward, and is especially prominent 
opposite the last two molar teeth; it affords attachment throughout its whole 
extent to the Mylohyoid muscle; the Superior constrictor of the pharynx with 
the pterygomandibular ligament being attached above its posterior extremity, near 
the alveolar margin. The portion of the bone above this ridge is smooth and 
covered by the mucous membrane of the mouth; the portion below presents an 
oblong depression, the submaxillary fossa (fovea submaxillaris) , wider behind than 
in front, for the lodgment of the submaxillary gland. The external and internal 
oblique lines divide the body of the bone into a superior or alveolar and an infe- 
rior or basilar portion. 

Borders. — ^The superior or alveolar portion of the body (pars alveolaris) has 
above a narrow border which is wider and the margins of which are thicker 
behind than in front. It is hollowed into numerous cavities (alveoli dentales), for 
the reception of the teeth ; these cavities are sixteen in number, and vary in depth 
and size according to the teeth which they contain. To the outer side of the alveo- 
lar border the Buccinator muscle is attached as far forward as the first molar tooth. 
The inferior or basilar portion (basis mandibulae) is rounded, longer than the superior 
and thicker in front tlian behind; it presents a shallow groove, just where the body 
joins the ramus, over wliich the facial artery turns. 

The Perpendicular Portions or Rami (rami mandibulae). — ^The perpendicular 
portions or rami are of a quadrilateral form. Each presents for examination two 
surfaces, four borders, and two processes. 

Surfaces. — The external surface is flat, marked with ridges, and gives attachment 
throughout nearly the whole of its extent to the Masseter muscle. 

The internal surface presents about its centre an oblique foramen (foramen man- 
dibulare), the beginning of the inferior dental canal, which transmits the inferior 
dental vessels and nerve. The margin of this opening is irregular; it presents 
in front a prominent ridge, surmounted by a sharp spine, the lingula (lingula 
mandibidae), which gives attachment to the internal lateral ligament of the 
mandible, and at its lower and back part a notch leading to a groove, the mylo- 
hyoidean groove (sulcus mylohyoideus) , which runs obliquely downward to the back 
part of the submaxillary fossa, and lodges the mylohyoid vessels and nerve. Be- 
hind the groove is a rough surface, for the insertion of the Internal pterygoid 
muscle. The inferior dental canal (canalis mandibulae) runs obliquely downward 
and forward in the substance of the ramus, and then horizontally forward in the 
body; it is here placed under the alveoli, with which it communicates by small 



118 SPECIAL ANATOMY OF THE SKELETON 

openings. On arriving at the incisor teeth, it turns back to communicate with the 
mental foramen, giving off two small canals, which run forward, to be lost in the 
cancellous tissue of the bone beneath the incisor teeth. This canal, in the poste- 
rior two-thirds of the bone, is situated nearer the internal surface of the jaw ; and 
in the anterior third, nearer its external surface. Its walls are composed of com- 
pact tissue at either extremity, and of cancellous in the centre. It contains the 
inferior dental vessels and nerve, from which branches are distributed to the teeth 
through small apertures at the bases of the alveoli. 

Borders. — ^The lower border of the ramus is thick, straight, and continuous with 
the body of the bone. At its junction with the posterior border is the angle of the 
jaw (angiilus mandihulae). The angle is either inverted or everted, and marked 
by rough, oblique ridges on each side, for the attachment of the Masseter externally 
and the Internal pterygoid internally; the stylomaxillary ligament is attached to 
the angle between these muscles. The anterior border is thin above, thicker below, 
and continuous with the external oblique line. The posterior border is thick, 
smooth, rounded, and covered by the parotid gland. The upper border of the 
ramus is thin, and presents two processes, separated by a deep concavity, the 
sigmoid notch. Of these processes, the anterior is the coronoid, the posterior, 
the condyloid. 

The coronoid process (processus coronoideus) is a thin, flat, triangular eminence, 
which varies in shape and size. Its anterior border is convex, and is continuous 
below with the anterior border of the ramus; its posterior border is concave, and 
forms the anterior boundary of the sigmoid notch. Its external surface is smooth, 
and affords attachment to the Temporal and Masseter muscles. Its internal 
surface gives insertion to the Temporal muscle, and presents a ridge which begins 
near the apex of the process and runs downward and forward to the inner side of 
the last molar tooth. Between this ridge and the anterior border is a grooved 
triangular area, the upper part of which gives attachment to the Temporal, the 
lower part to some fibres of the Buccinator. 

The condyloid process (^processus condyloideus), shorter but thicker than the 
coronoid, consists of two portions, the condyle (capitulum mandihulae), and the 
constricted portion which supports the condyle, the neck [collum mandihulae). 
The condyle is of an oblong form, its long axis being transverse, and set obliquely 
on the neck in such a manner that its outer end is a little more forward and a little 
higher than its inner. It is convex from before backward and from side to side, 
the articular surface extending farther on the posterior than on the anterior aspect. 
At its outer extremity is a small tubercle for the attachment of the external lateral 
ligament of the temporomandibular joint. The neck of the condyle is flattened 
from before backward, and strengthened by ridges which descend from the fore 
part and sides of the condyle. Its lateral margins are narrow, the external one 
giving attachment to part of the external lateral ligament. Its posterior surface 
is convex; its anterior is hollowed out on its inner side by a depression, the ptery- 
goid depression (fovea pterygoidea), for the attachment of the External pterygoid 
muscle. 

The sigmoid notch (incisura inandihulae), separating the two processes, is a 
deep semilunar depression, crossed by the masseteric vessels and nerve. 

Development. — The mandible is ossified in the fibrous membrane covering the outer surfaces 
of Meckel's cartilages. These cartilages, one on either side, form the cartilaginous bar of the 
mandibular arch, being joined at the symphysis by mesodermal tissue. The proximal end of 
each cartilage is connected with the periotic capsule, and here serves to form the malleus and 
incus. The next succeeding portion as far as the lingula is replaced by fibrous tissue to form 
the sphenomandibular ligament. Between the lingula and the canine tooth the cartilage disap- 
pears, while the portion near the symphysis becomes ossified and incorporated with the incisor 
division of the mandible. This ossific centre appears in about the sixth week of fetal life — i. e., 
earlier than in any other bone except the clavicle; ossification is practically complete by the tenth 



THE MANDIBLE, OR LO WEB JA W \ 19 

week. Accessory nuclei develop to form the condyle and the coronoid process, in the front part 
of both alveolar walls and along the front of the lower border of the bone. 

These accessory nuclei possess no separate ossific centres, but ossification extends into them 
from the adjacent membrane bone and they undergo absorption. The inner alveolar border, 
usually described as arising from a separate ossific centre {splenial centre), is formed in the human 
mandible by an ingrowth from the main mass of the bone. At birth the bone consists of two 
halves, united by a fibrous symjihysis, in which ossification takes place during the first year. 

Articulation. — With the glenoid fossse of the two temporal bones. 

Attachment of Muscles. — To fifteen -pairs — to its external surface, commencing at the sym- 
physis, and proceeding backward: Levator menti, Depressor labii inferioris, Depressor anguli 
oris, Platysma, Buccinator, Masseter; a portion of the Orbicularis oris is also attached to this 
surface. To its internal surface, commencing at the same point: Geniohyoglossus, Geniohyoirl, 
Mylohyoid, Digastric, Superior constrictor, Temporal, Internal pterygoid, External pterygoid. 



Meckel's cartilage 



Fic. SS. — Scheme showing ossification of the mandible, inner side (Low). The membrane bone is colored 
red. The greater part of Meckel's cartilage is colored blue. The upturned, stippled portion near the symphysis 
represents the part of Meckel's cartilage, which is surrounded and invaded by the membrane bone. The accessory 
nuclei of cartilage in the condyle, coronoid process, alveolar border, and body are indicated by stippled areas. 





Fig. 89. — Scheme showing ossification of mandible from the outer side (Low). Membrane bone colored red. 
Accessory nuclei of cartilage stippled. 

CHANGES PRODUCED IN THE MANDIBLE BY AGE. 

The changes which the mandible undergoes after birth relate (1) to the alterations effected 
in the body of the bone by the first and second dentitions, the loss of the teeth in the aged, and 
the subsequent absorption of the alveoli; (2) to the size and situation of the dental canal; and 
(3) to the angle at which the ramus joins with the body. 

At birth (Fig. 90) the bone consists of lateral halves, united by fibrous tissue. The body is 
a mere shell of bone, containing the sockets of the two incisor, the canine, and the two tem- 
porary molar teeth, imperfectly partitioned from one another. The dental canal is of large size, 
and runs near the lower border of the bone, the mental foramen opening beneath the socket of 
the first molar. The angle is obtuse (17.5 degrees), and the condyloid portion nearly in the 
same horizontal line with the body; the neck of the condyle is short, and bent backward. The 
coronoid process is of comparatively large size, and situated at right angles with the rest of 
the bone. 

SIDE VIEW OF THE MANDIBLE AT DIFFERENT PERIODS OF LIFE. 

After birth (Fig. 91) the two segments of the bone become joined at the symphysis, from 
below upward, in the first year; but a trace of separation may be visible in the beginning of the 
second year near the alveolar margin. The body becomes elongated in its whole length, but 
more especially behind the mental foramen, to provide space for the three additional teeth 
developed in this part. The depth of the body becomes greater, owing to increased growth of 
the alveolar part, to afford room for the fangs of the teeth, and by thickening of the subdental 
portion, which enables the jaw to withstand the powerful action of the masticatory muscles; but 
the alveolar portion is the deeper of the two, and, consequently, the chief part of the body lies 
above the oblique line. The dental canal after the second dentition is situated just above the 
level of the mylohyoid ridge, and the mental foramen occupies the position usual to it in the 
adult. The angle becomes less obtuse, owing to the separation of the jaws by the teeth. (About 
the fourth year it is 140 degrees.) 



120 



SPECIAL ANA TOMY OF THE SKELETON 





Fig. 90. — Mandible in newborn. 



Fig. 91. — In child six to seven years of age. 




Fig. 92. — In the adult. 




Fig. 93.— In old age. (Spalteholz.) 



THE SUTURES 121 

In the adult (Fig. 92) the alveolar and basilar portions of the body are usually of equal dejjth. 
The mental foramen opens midway between the upper and lower border of the bone, and the 
dental canal runs nearly parallel with the mylohyoid line. The ramus is almost vertical in 
direction, and joins the body nearly at right angles. 

In old age (Fig. 93) the bone becomes greatly reduced in size; for with the loss of the teeth 
the alveolar process is absorbed, and the basilar part of the bone alone remains, conseciuently, 
the chief part of the bone is heloiv the oblique line. The dental canal, with the mental foramen 
opening from it, is close to the alveolar liorder. The rami are oblique in direction, the angle 
obtuse, and the neck of the condyle more or less bent backward. 



The Sutures. 

The bones of the cerebral cranium and face are connected to each other by means 
of sutures. That is, the articulating surfaces or edges of the bones are more or 
less roughened or uneven, and are closely adapted to each other, a small amount 
of intervening fibrous tissue, the sutiual ligament, fastening them together. The 
cranial sutures may be divided into three sets: (1) Those at the vertex of the skull. 
(2) Those at the side of the skull. (3) Those at the base. 

The sutures at the vertex of the skull are four — the metopic, the sagittal, the 
coronal, and the lambdoid. 

The metopic or frontal suture (sutiira frontalis) (Fig. 44) is usually noted in 
adults as a trivial fissure, just above the glabella. At birth the two halves of the 
frontal bone are separated by the suture. This suture is, as a rule, almost com- 
pletely or completely closed during the fifth or sixth year, but occasionally it 
persists throughout life. 

The interparietal or sagittal suture {sutura sagittalis) is formed by the junction 
of the two parietal bones, and extends from the middle of the frontal bone back- 
ward to the superior angle of the occipital. This suture is sometimes perforated, 
near its posterior extremity, by the parietal foramen; and in front, where it joins 
the coronal suture, a space is occasionally left which encloses a large Wormian 
bone. 

The frontoparietal or coronal suture (sutura coronalis) (Fig. 99) extends trans- 
versely across the vertex of the skull, and connects the frontal with the parietal 
bones. It commences at the extremity of the greater wing of the sphenoid on one 
side, and terminates at the same point on the opposite side. The dentations of the 
suture are more marked at the sides than at the summit, and are so constructed 
that the frontal rests on the parietal above, while laterally the frontal supports 
the parietal. 

The occipitoparietal or lambdoid suture (sutura lamhdoidea) (Fig. 99), so called 
from its resemblance to the Greek letter A, connects the occipital with the parietal 
bones. It commences on each side at the mastoid portion of the temporal bone, 
and inclines upward to the end of the sagittal suture. The dentations of this 
suture are very deep and distinct, and are often interrupted by several small 
Wormian bones. 

The lateral sutures (Fig. 99) extend from the external angular process of the 
frontal bone to the lower end of the lambdoid suture behind. The anterior 
fortion is formed between the lateral part of the frontal bone above and the 
malar and greater wing of the sphenoid below, forming the frontomalar suture 
(sutura zygomaticofrontalis) and frontosphenoidal suture (sutura sphenofrontal is). 
These sutures can also be seen in the orbit, and form part of the so-called 
transverse facial suture. The posterior portion is formed between the parietal 
bone above and the greater wing of the sphenoid, the squamous and mastoid 
portions of the temporal bone below, forming the sphenoparietal, squamoparietal, 
and mastoparietal sutures. 



122 SPECIAL ANA TOMY OF THE SKELETON 

The sphenoparietal (sutura sphenopariefalis) is very short; it is formed by the 
tip of the greater wing of the sphenoid, which overlaps the anterior inferior angle 
of the parietal bone. 

The squamoparietal (sutura squamosa) is arched, and is formed by the squamous 
portion of the temporal bone overlapping the middle division of the lower border 
of the parietal. 

The mastoparietal (sutura parietmnastoidea), a short suture, deeply dentated, 
is formed by the posterior inferior angle of the parietal and the superior border of 
the mastoid portion of the temporal. 

The sutures at the base of the ^kull (Fig. 98) are the basilar in the centre, and on 
each side the petro-occipital, the masto-occipital, the petrosphenoidal, and the 
squamosphenoidal. 

The basilar suture (Jissura spheiwoccipitalis) is formed by the junction of the 
basilar surface of the occipital bone with the posterior surface of the body of 
the sphenoid. At an early period of life a thin plate of cartilage exists between 
these bones, but in the adult they become fused into one (synchondrosis spheno- 
occipitalis). Between the outer extremity of the basilar suture and the termina- 
tion of the lambdoid an irregular suture exists, which is subdivided into two por- 
tions. The inner portion, formed by the union of the petrous part of the temporal 
with the occipital bone, is termed the petro-occipital fissure (fissiira petrooccipitalis). 
The outer portion, formed by the junction of the mastoid part of the temporal 
with the occipital, is called the masto-occipital suture (sutura occipitomastoidea) . 
Between the bones forming the petro-occipital suture a thin plate of cartilage exists; 
in the masto-occipital is occasionally found the opening of the mastoid foramen. 
Between the outer extremity of the basilar suture and the sphenoparietal an irregu- 
lar suture may be seen, formed by the union of the sphenoid with the temporal 
bone. The inner and smaller portion of this suture is termed the petrosphenoidal 
fissure (fissura sphenopetrosal; it is formed between the petrous portion of the 
temporal and the greater wing of the sphenoid; the outer portion, of greater 
length and arched, is formed between the squamous portion of the temporal and 
the greater wing of the sphenoid; it is called the squamosphenoidal suture (sutura 
sphenosquamosa). 

The bones of the cerebral cranium are connected with those of the face, and the 
facial bones with each other, by numerous sutures, which, though distinctly 
marked, have received no special names. The only remaining suture deserving 
especial consideration is the transverse suture. This extends across the upper part 
of the face, and is formed by the junction of the frontal with the facial bones; it 
extends from the external angular process of one side to the same point on the 
opposite side, and connects the frontal with the malar, the sphenoid, the ethmoid, 
the lacrimal, the maxillae, and the nasal bones on each side (suiura zygomatico- 
jrontalis; the orbital portion of the sutura sphenofrontalis, sutura frontoethmoidalis, 
sutura frontolacrimalis, sutura frontomaxillaris, sutura nasofrontalis) . 

The sutures remain separate for a considerable period after the complete for- 
mation of the skull. It is probable that they serve the purpose of permitting the 
growth of the bones at their margins, while their peculiar formation, together 
with the interposition of the sutural ligament between the bones forming them, 
prevents the dispersion of blows or jars received upon the skull. Humphry 
remarks, "that, as a general rule, the sutures are first obliterated at the parts in 
which the ossification of the skull was last completed — viz., in the neighborhood 
of the fontanelles; and the cranial bones seem in this respect to observe a similar 
law to that which regulates the union of the epiphyses to the shafts of the long 
bones." The same author remarks that the time of their disappearance is 
extremely variable; they are sometimes found well marked in skulls edentulous 
with age, while in others which have only just reached maturity they can hardly 



THE SKULL AS A WHOLE \ 23 

be traced. The obliteration of the sutures takes place sooner on the inner ihun 
"on the outer surface of the skull. The sagittal and coronal sutures are, as a rule, 
the first to become ossified — the process starting near the posterior extremity of 
the former and the lower ends of the latter. 



THE SKULL AS A WHOLE. 

The skull, formed by the union of the several cranial and facial bones already 
described, when considered as a whole is divisible into five regions — a superior 
region or vertex, an inferior region or base, two lateral regions, and an anterior 
region, the face. 

The Vertex of the Skull. — The superior region, or vertex, presents two sur- 
faces, an external and an internal. 

Surfaces. — The external surface {norma verticalis) is bounded, in front, by the 
glabella and superciliary ridges; behind, by the occipital protuberance and superior 
curved lines of the occipital bone; laterally, by an imaginary line extending from 
the outer end of the superior curved line, along the temporal ridge, to the external 
angular process of the frontal bone. This surface includes the greater part of 
the vertical portion of the frontal, the greater part of the parietal, and the superior 
third of the occipital bone; it is smooth, convex, of an elongated oval form, crossed 
transversely by the coronal suture, and from before backward by the sagittal, 
which terminates behind in the lambdoid. The point of junction of the coronal 
and sagittal sutures is named the bregma. The point of junction of the sagittal 
and lambdoid sutures is called the lambda, and is about 2f inches (7 cm.) above 
the external occipital protuberance. From before backward may be seen the 
frontal eminences and remains of the suture connecting the two lateral halves of 
the frontal bone; on each side of the sagittal suture are the parietal foramen and 
parietal eminence, and still more posteriorly the convex surface of the occipital 
bone. In the neighborhood of the parietal foramen the skull is often flattened, 
and the name of obelion is sometimes given to that point of the sagittal suture 
which lies exactly opposite to the parietal foramen. 

The internal or cerebral surface is concave, presents depressions for the convolu- 
tions of the cerebrum, and numerous furrows for the lodgement of branches of the 
meningeal arteries. Along the middle line of this surface is a longitudinal groove, 
narrow in front, where it commences at the frontal crest, but broader behind, 
where it lodges the superior longitudinal sinus, and by its margin affords attachment 
' to the falx cerebri. On either side of it are several depressions for the arachnoid 
villi, and at its back part the internal openings of the parietal foramina. This 
surface is crossed, in front, by the coronal suture; from before backward by the 
sagittal; behind, by the lambdoid. 

The Base of the Skull (the Skull being without the Mandible).— The 
inferior region, or base of the skull, presents two surfaces — an internal or cerebral, 
and an external or basilar. 

Siu'faces.— The internal or cerebral surface (Fig. 94) presents three fossa:", called 
the anterior, middle, and posterior fossw of the cranium. 

The anterior fossa (fossa cranii aiiterior) (Fig. 94) is formed by the orliital plates 
of the frontal, the cribriform plate of the ethmoid, the anterior third of the superior 
surface of the body, and the upper surface of the lesser wings of the sphenoid bone, 
and is situated at a higher level than the other fosste. It is the most elevated of the 
three fosste, convex externally where it corresponds to the roof of the orbit, con- 
cave in the median line in the situation of the cribriform plate of the ethmoid. 
It is traversed on either side by three sutures, the ethmofrontal, ethmosphenoidal, 
and frontosphenoidal, and lodges the frontal lobes of the cerebrum. It presents. 



124 SPECIAL ANATOMY OF THE SKELETON 

in the median line, from before backward, the commencement of the groove for 
the superior sagittal sinus and the frontal crest for the attachment of the falx cerebri; 



Groove for superior sagittal sinus. 

Gi'OOves for anterior meningeal artery. 

Foramen csecum. 

Crista galli. 

Slit for nasal nerve. 

Groove for nasal nerve. 

Anterior ethmoidal foramen. 

Orifices for olfactory nerves. 

Posterior ethmoidal foramen. 

Ethmoidal spine. 



Olfactory grooves. 

Optic foramen.. 

Optic groove. 

Olivary process. 

Anterior clinoid process. 

Middle clinoid process. 

PosteHor clinoid process. 

Groove for 6th nerve. 

Foramen lacerum medinm. 

OHfiee of carotid canal. 

ion for Gasserian ganglion. 



Deprei 



Meatus auditorius inter 

Floccular fossa. 

Superior petrosal groove. 

Foramen lacerum posterius. 

Anterior condylar forarnen. 

Aquxducius vesiUndi. 

Posterior condylar foramen. 



i foramen. 
Posterior meningeal grooves. 




Fig. 94. — Base of the skull. Inner or cerebral surface. 



the foramen cecum, an aperture formed between the frontal bone and the crista 
gaUi of the ethmoid, which, if pervious, transmits a small vein from the nose to 
the sagittal sinus; behind tlae foramen cecum, the crista galli, the posterior mar- 



THE SKULL AS A WHOLE 



125 



gin of which affords attachment to the falx cerebri; on either side of the crista 
gaili, the cribriform plate, which supports the olfactory bulb, and presents three 
rows of foramina for the transmission of its nerve filaments, and in front a slit- 
like opening {nasal slit) for the nasal branch of the ophthalmic division of the 
trigeminal nerve. On the outer side of each olfactory groove are the internal 
openings of the anterior and posterior ethmoidal foramina, the former situated about 
the middle of the outer margin of the olfactory groove. The anterior ethmoidal 
foramen transmits the anterior ethmoidal vessels and the nasal nerve, which latter 
runs in a depression along the surface of the ethmoid to the slit-like opening 
above mentioned ; while the posterior ethmoidal foramen opens at tlie })ack part 
of this margin under cover of the projecting lamina of the sphenoid, and trans- 
mits the posterior ethmoidal vessels. Farther back in the middle line is the eth- 
moidal spine, bounded behind by a slight elevation, separating two shallow longi- 




FiG. 95. — Base of the skull. Interior view. 



tudinal grooves which support the olfactory lobes. Behind this is a transverse 
sharp ridge, running outward on either side to the anterior margin of the optic 
foramen, and separating the anterior from the middle fossa of the base of the skull. 
The anterior fossa presents, laterally, depressions for the convolutions of the cere- 
brum and grooves for the lodgement of the anterior meningeal arteries. 

The middle fossa (fossa cranii media) (Fig. 94), deeper than the preceding, is 
narrow in the middle line, but becomes wider at the side of the skull. It is bounded in 
front by the posterior margin of the lesser wings of the sphenoid, the anterior clinoid 
processes, and the ridge forming the anterior margin of the optic groove; behind, 
by the superior border and anterior surface of the petrous portions of the temporal 
and the dorsum sellse; externally, by the squamous portions of the temporal and 
the anterior inferior angle of the parietal bones and greater wings of the sphenoid. 
On each side it is traversed by four sutures, the squamoparietal, sphenoparietal, 



126 



SPECIAL ANATOMY OF THE SKELETON 



squamosphenoidal, and petrosphenoidal. In the middle line, from before back- 
ward, is the optic groove, which supports the optic commissure; the groove terminates 
on each side in the optic foramen, for the passage of the optic nerve and ophthal- 
mic artery; behind the optic groove is the olivary process and laterally the anterior 
clinoid processes, to which are attached processes of the tentorium cerebelli. 
Farther back is the sella turcica, a deep depression which lodges the hypophysis 
and circular sinus, bounded in front by a small eminence on either side, the middle 
clinoid process, and behind by a broad, square plate of bone, the dorsum sellae, 
surmounted at each superior angle by a tubercle, the posterior clinoid process; 
beneath the latter process is a notch, for the abducent nerve. On each side of 
the sella turcica is the carotid groove; it is broad, shallow, and curved somewhat 
like the italic letter /,• it commences behind at the foramen lacerum medium, and 




Fig. 96. — Median sagittal section of tlie skull. 



terminates on the inner side of the anterior clinoid process, and presents along its 
outer margin a ridge of bone, the lingula. This groove lodges the cavernous 
sinus, the internal carotid artery, and the nerves which enter the orbit. The 
sides of the middle fossa are of considerable depth; they present depressions for 
the convolutions of the cerebrum and grooves for the branches of the middle men- 
ingeal artery; the latter commence on the outer side of the foramen spinosum, and 
consist of two large branches, an anterior and a posterior; the former passing 
upward and forward to the anterior inferior angle of the parietal bone, the latter 
passing upward and backward. The following foramina may also be seen on 
either side from before backward. Most anteriorly is seen the sphenoidal fissure 
{foramen lacerum ajiterius), formed above by the lesser wing of the sphenoid; 
below^ by the greater wing; internally, by the body of the sphenoid; and some- 



THE SKULL AS A WHOLE 127 

times completed externally by the orbital plate of the frontal bone. It trans- 
mits the third, the fourth, the three branches of the ophthalmic division of 
the trigeminal, the abducent nerve, some filaments from the cavernous plexus 
of the sympathetics, the orbital branch of the middle meningeal artery, a recurrent 
branch from the lacrimal artery to the dura, and the ophthalmic vein. Behind 
the inner extremity of the sphenoidal fissure is the foramen rotundum, for the passage 
of the second division of the trigeminal nerve ; still more posteriorly is seen a small 
orifice, the foramen Vesalii, an opening situated between the foramen rotundum 
and the foramen ovale, a little internal to both; it varies in size in dift'erent indi- 
viduals, and is often absent; when present it transmits a small vein and opens below 
into the outer side of the scaphoid fossa. Behind and external to the latter open- 
ing is the foramen ovale, which transmits the third division of the trigeminal nerve, 
the small meningeal artery, and sometimes the small petrosal nerve. On the 
outer side of the foramen ovale is the foramen spinosum, for the passage of the middle 
meningeal artery; occasionally a small foramen (canaliculus innominatus) for the 
transmission of the small superficial petrosal nerve is seen internal to the fora- 
men spinosum. On the inner side of the foramen ovale is the foramen lacerum 
medium ( foramen lacerum) ; the lower part of this aperture is filled in the recent 
state with cartilage which is pierced by the Vidian nerve and a meningeal branch 
from the ascending pharyngeal artery. On the anterior surface of the petrous 
portion of the temporal bone is seen, from without inward, the eminence caused 
by the projection of the superior semicircular canal ; in front of and a little outside 
this is a depression, the tegmen tympani, corresponding to the roof of the tympa- 
num; the groove leading to the hiatus Fallopii, for the transmission of the greater 
petrosal nerve and the petrosal branch of the middle meningeal artery; beneath 
it, a smaller groove, for the passage of the lesser petrosal nerve; and, near the apex 
of the bone, the depression for the Gasserian ganglion; and the internal orifice 
of the carotid canal, for the passage of the internal carotid artery and carotid 
plexus of nerves. 

The posterior fossa ( fossa cranii posterior) , deeply concave, is the largest of the 
three, and situated on a lower level than either of the preceding. It is formed by 
the posterior third of the superior surface of the body of the sphenoid, by the 
occipital, the posterior surface of the petrous and the mastoid portions of the tem- 
poral, and the posterior inferior angle of the parietal bones; it is crossed on either 
side by four sutures, the petro-occipital, the masto-occipital, the mastoparietal, 
and the basilar; and lodges the cerebellum, pons, and medulla oblongata. It is 
separated from the middle fossa in the median line by the dorsum sellee, and on 
each side by the superior border of the petrous portion of the temporal bone. This 
border serves for the attachment of the tentorium cerebelli, is grooved for the supe- 
rior petrosal sinus, and at its inner extremity presents a notch, in which rests the 
trigeminal nerve. The circumference of the fossa is bounded posteriorly by the 
grooves for the lateral (transverse) sinuses. In the centre of this fossa is the fora- 
men magnum, bounded on either side by a rough tubercle, which gives attachment 
to the odontoid or cheek ligaments; and a little above these are seen the internal 
openings of the anterior condylar foramina,through which pass the hypoglossal ner\'e 
and meningeal branches from the ascending pharyngeal arteries. In front of the 
foramen magnum is a grooved surface, formed by the basilar process of the occipi- 
tal bone and by the posterior third of the superior surface of the body of the sphe- 
noid, which supports the medulla oblongata and pons; and articulates on each side 
with the petrous portion of the temporal bone, forming the petro-occipital suture, 
the anterior half of which is grooved for the inferior petrosal sinus, the posterior 
half being encroached upon by the foramen lacerum posterius {foramen jugulare). 
This foramen presents three compartments — through the anterior passes the infe- 
rior petrosal sinus; through the posterior, the lateral sinus and some meningeal 



128 SPECIAL ANATOMY OF THE SKELETON 

branches from the occipital and ascending pharyngeal arteries; and through the 
middle, the glossopharyngeal, vagus, and spinal accessory nerves. Above the jugu- 
lar foramen is the internal auditory meatus, for the facial and auditory nerves and 
auditory artery; behind and external to this is the slit-like opening leading into the 
aquaeductus vestibuli, which lodges the ductus endolymphaticus; while between 
the two latter, and near the superior border of the petrous portion, is a small, tri- 
angular depression, the remains of the floccular fossa, which lodges a process of the 
dura and occasionally transmits a small vein from the substance of the bone. Be- 
hind the foramen magnum are the inferior occipital fossae, which lodge the hemi- 
spheres of the cerebellum, separated from each other by the internal occipital 
crest, which serves for the attachment of the falx cerebelli and lodges the 
occipital sinus. The posterior fossae are limited above by the deep transverse 
grooves for the lodgment of the lateral sinuses, which diverge forward on each 
side from a depression in the mesal plate, the torcular. These channels, in their 
passage outward, groove the occipital bone, the posterior inferior angles of the 
parietals, the mastoid portions of the temporals, and the jugular processes of 
the occipital, and terminate at the back part of the jugular foramen. Where the 
lateral sinus grooves the mastoid portion of the temporal bone (sigmoid fossa) 
the orifice of the mastoid foramen may be seen. Just previous to the termination 
of the groove the posterior condylar foramen opens into it. Neither foramen is 
constant. 

The basilar surface (norma basalis) (Fig. 97) of the skull is extremely irregular. 
It is bounded in front by the incisor teeth in the maxillae; behind by the inion and 
the superior curved lines of the occipital bone; and laterally by the alveolar arch, 
the lower border of the malar bones, the zygoma, and an imaginary line extending 
from the zygoma to the mastoid process and extremity of the superior curved line 
of the occiput. It is formed by the palatal processes of the maxillae and palate 
bones, the vomer, the pterygoid processes, under surface of the greater wings, 
spinous processes and part of the body of the sphenoid, the under surface of the 
squamous, mastoid, and petrous portions of the tempoi'als, and the under surface of 
the occipital bone. The anterior part of the base of the skull is raised above the 
le\el of the rest of this surface (when the skull is turned over for the purpose of 
examination), is surrounded by the alveolar process, which is thicker behind than 
in front, and excavated by sixteen depressions for the lodgement of the teeth of 
the maxillae, the cavities varying in depth and size according to the teeth they con- 
tain. Immediately behind the incisor teeth is the anterior palatine fossa. At the 
bottom of this fossa may usually be seen four apertures, two placed laterally, the 
foramina of Stenson, which open above, one in the floor of each nostril, and trans- 
mit the anterior branch of the posterior palatine vessels, and two in the median 
line in the intermaxillary suture, the foramina of Scarpa, one in front of the other, 
the anterior transmitting the left, and the posterior (the larger) the right, naso- 
palatine nerve. These two lateral canals are sometimes wanting, or they may 
join to form a single one, or one of them may open into one of the lateral canals 
above referred to. The palatine vault is concave, uneven, perforated by numerous 
foramina, marked by depressions for the palatine glands, and crossed by a crucial 
suture, formed by the junction of the four bones of which it is composed. At the 
front part of this surface a delicate linear suture may frequently be seen, passing 
outward and forward from the anterior palatine fossa to the interval between the 
lateral incisor and canine teeth, and marking off the premaxillary portion of the 
bone. At each posterior angle of the hard palate is. the posterior palatine foramen, 
for the transmission of the posterior palatine vessels and great descending palatine 
nerve; and running forward and inward from it a groove, for the same vessels and 
nerve. Behind the posterior palatine foramen is the tuberosity of the palate bone, 
perforated by one or more accessory posterior palatine canals, giving passage to the 



THE SKULL AS A WHOLE 



129 



middle and posterior palatine nerves from the sphenopalatine (Meckel's) ganglion, 
and marked by the commencement of a ridge which runs transversely inward, 



Anterior palatine fossa. 

Transmits left nasopalatine nerve. 
Transmits anterior palatine vessel. 
Transmits right nasopalatine nerve. 



Accessory palatine foramina. 



■Sphenoid process of palate. 
Pterygopalatine canal. 




Fig. 97. — Base of the skuU. E.xternal surface. 
9 



130 



SPECIAL ANATOMY OF THE SKELETON 



and serves for the attachment of the tendinous expansion of the Tensor palati 
muscle. Projecting backward from the centre of the posterior border of the hard 
palate is the posterior nasal spine, for the attachment of the Azygos uvulae muscle. 
Behind and above the hard palate is the posterior aperture of the nasal fossae 
(choanse), divided into two parts by the vomer, bounded above by the body of 
the sphenoid, below by the horizontal plate of the palate bone, and laterally 
by the internal pterygoid plate of the sphenoid. Each aperture measures about 
an inch in the vertical and about half an inch in the transverse direction. At the 
base of the vomer may be seen the expanded alse of this bone, receiving between 
them the rostrum of the sphenoid. Near the lateral margins of the vomer, at the 
root of the pterygoid processes, are the pterygopalatine canals, which transmit the 
pterygopalatine vessels and the pharyngeal nerve from the sphenopalatine 
(Meckel's) ganglion. The pterygoid process, which bounds the posterior nares 
on each side, presents near its base the pterygoid or Vidian canal, for the Vidian 
nerve and artery. Each process consists of two plates, which bifurcate at the 
extremity to receive the tuberosity of the palate bone, and are separated behind 
by the pterygoid fossa, which lodges the Internal pterygoid muscle. The internal 




Fig. 98.— Base of the skull. External surface. 



plate is long and narrow, presenting on the border of its base the scaphoid fossa, 
for the origin of the Tensor palati muscle, and at its extremity the hamular process, 
around which the tendon of this muscle turns. The external pterygoid plate is 
broad, forms the inner boundary of the zygomatic fossa, and affords attachment by 
its outer surface to the External pterygoid muscle. 

Behind the nasal fossse in the middle line is the basilar surface of the occipital 



THE SKULL AS A WHOLE 131 

bone, presenting in its centre the pharyngeal spine, for the attachment of the 
Superior constrictor muscle of the pharynx, with depressions on each sifle for 
the insertion of the Rectus capitis anticus major and minor. At the base of the 
external pterygoid plate is the foramen ovale, for the transmission of the third divi- 
sion of the trigeminal nerve, the small meningeal artery, and sometimes the small 
petrosal nerve; behind this, the foramen spinosum, which transmits the middle 
meningeal artery, and the prominent spinous process of the sphenoid, which gi\es 
attachment to the internal lateral ligament of the mandible and the Tensor palati 
muscle. External to the spinous process is the glenoid fossa, divided into two parts 
by the Glaserian fissure (page 88), the anterior portion concave, smooth, bounded 
in front by the eminentia articularis, and serving for the articulation of the condyle 
of the mandible; the posterior portion rough, bounded behind by the tympanic 
plate, and serving for the reception of part of the parotid gland. Emerging from 
between the laminae of the vaginal process of the tympanic plate is the styloid 
process, and at the base of this process is the stylomastoid foramen, for the exit of 
the facial nerve and entrance of the stylomastoid artery. External to the stylo- 
mastoid foramen is the auricular fissure, for the exit of the auricular branch of the 
vagus, bounded behind by the mastoid process. Upon the inner side of the mas- 
toid process is a deep groove, the digastric fossa; and a little more internally the 
occipital groove, for the occipital artery. At the base of the internal pterygoid plate 
is a large and somewhat triangular aperture, the foramen lacerum medium, bounded 
in front by the greater wing of the sphenoid, behind by the apex of the petrous por- 
tion of the temporal bone, and internally by the body of the sphenoid and basilar 
process of the occipital bone; it presents in front the posterior orifice of the Vidian 
canal; behind, the aperture of the carotid canal. The basilar surface of this open- 
ing is filled in the recent state by fibrocartilaginous substance, which is pierced 
by the Vidian nerve and a meningeal branch of the ascending pharyngeal artery; 
across its upper or cerebral aspect passes the internal carotid artery. External to 
this aperture the petrosphenoidal suture is observed, at the outer termination of 
which is seen the orifice of the canal for the Eustachian tube and that for the Ten- 
sor tympani muscle. Behind this suture is seen the under surface of the petrous 
portion of the temporal bone, presenting from within outward, the quadrilateral, 
rough surface, part of which affords attachment to the Levator palati and Tensor 
tympani muscles; posterior to this surface is the orifice of the carotid canal and the 
orifice of the aquaeductus cochleae, the former transmitting the internal carotid 
artery and the ascending branches of the superior cervical ganglion of the sympa- 
thetic, the latter serving for the passage of a small artery to and a small vein from 
the cochlea. Behind the carotid canal is a large aperture, the jugular foramen, 
formed in front by the petrous portion of the temporal, and behind by the occipital; 
it is generally larger on the right than on the left side, and is divided into three 
compartments by processes of dura. The anterior is for the passage of the inferior 
petrosal sinus; the posterior, for the lateral sinus and some meningeal branches from 
the occipital and ascending pharyngeal arteries; the central one, for the glosso- 
pharyngeal, vagus, and spinal accessory nerves. On the ridge of the bone dividing 
the carotid canal from the jugular foramen is the small foramen for the transmis- 
sion of Jacobson's nerve (tympanic branch of the glossopharyngeal) ; and on the 
wall of the jugular foramen, near the root of the styloid process, is the small aper- 
ture for the transmission of the auricular branch of the vagus nerve (Arnold's 
nerve) . Behind the basilar surface of the occipital bone is the foramen magnum, 
bounded on each side by the condyles, rough internally for the attachment of the 
check ligaments, and presenting externally a rough surface, the jugular process, 
which serves for the attachment of the Rectus capitis lateralis muscle and the lat- 
eral occipito-atlantal ligament. The middle of the anterior margin of the foramen 
magnum is called the basion. The mid-point of the posterior margin is called the 



132 



SPECIAL ANATOMY OF THE SKELETON 



opisthion. On either side of each condyle anteriorly is the anterior condylar fossa, 
continued as the anterior condylar foramen, for the passage of the hypoglossal 
nerve and often a meningeal branch of the ascending pharyngeal artery. Behind 
each condyle is the posterior condylar fossa, continued as the posterior condylar 
foramen, for the transmission of a vein to the lateral sinus. Behind the foramen 
magnum is the external occipital crest, terminating above at the external occipital 
protuberance, while on each side are seen the superior and inferior curved lines; 
these, as well as the surfaces of bone between them, are rough for the attachment 
of the muscles, which are enumerated on pages 70 and 71. 

The Lateral Region of the Skull. — The norma lateralis is of a somewhat 
triangular form, the base of the triangle being formed by a line extending from the 
external angular process of the frontal bone along the temporal ridge backward to 
the outer extremity of the superior curved line of the occiput; and the sides by 
two lines, the one drawn downward and backward from the external angular 
process of the frontal bone to the angle of the mandible, the other from the angle 
of the mandible upward and backward to the outer extremity of the superior 
curved line. This region is divisible into three portions — temporal fossa, mastoid 
portion, and zygomatic or infratemporal fossa. 




Fig. 99. — Lateral aspect of the skull. 



The Temporal Fossa (fossa temporalis). — The temporal fossa is bounded above 
and behind by the temporal ridges, which extend from the extei-nal angular process 
of the frontal upward and backward across the frontal and parietal bones, curving 
downward behind to terminate in the posterior root of the zygomatic process. In 
front it is bounded by the frontal, malar, and greater wing of the sphenoid ; externally 
by the zygomatic arch formed conjointly by the malar and temporal bones; heloiD, 
it is separated from the zygomatic fossa by the pterygoid ridge, seen on the outer 



THE SKULL AS A WHOLE 



1.3:3 



surface of the greater wing of the sphenoid. This fossa is formed by five bones, 
part of the frontal, greater wing of the sphenoid, parietal, squamous portion of the 
temporal and malar bones, and is traversed by six sutures, part of the frontomalar, 
sphenomalar, coronal, sphenoparietal, squamoparietal, and squamosphenoidal. 
The point where the coronal suture crosses the superior temporal ridge is named 
the stephanion; and the region where the four bones, the parietal, the frontal, 
the squamous portion of the temporal, and the greater wing of the sphenoid, 
meet, at the anterior inferior angle of the parietal bone, is named the pterion. 
This point is about on a level with the external angular process of the froii(<d 
bone and about one and a half inches (-3.75 cm.) behind it. This fossa is deeply 
concave in front, convex behind, traversed by grooves which lodge branches of 
the deep temporal arteries, and filled by the Temporal muscle. 

The Mastoid Portion. — The mastoid portion of the side of the skull is bounded 
in front by the anterior root of the zygoma; above, by a line which runs from the 
posterior root of the zygoma to the end of the mastoparietal suture; behind and 
below by the masto-occipital suture. It is formed by the mastoid and part of the 
squamous and petrous portions of the temporal bone; its surface is convex and 
rough for the attachment of muscles, and presents, from behind forward, the 
mastoid foramen, the mastoid process, the external auditory meatus surrounded by 




External auditory meatus 
Tympanicplate 



Spheno-inii.ciUary fissure 

Infra- temporal crest 
Pterygo-inaxillary fissure 

Hamidar process 



Styloid process 
Glenoid cavity 

Zygomatic process (cut) 



External pterygoid plate 
Fig. 100. — Left zygomatic fossa. 

the tympanic plate, and, most anteriorly, the temporomandibular articulation. The 
point where the posterior inferior angle of the parietal meets the occipital and 
mastoid portion of the temporal is named the asterion. 

The Zygomatic Fossa {fossa infratemporaUs). — The zygomatic fossa is an irregu- 
larly shaped cavity, situated below and on the inner side of the zygoma ; bounded in 
front by the zygomatic surface of the maxilla and the ridge which descends from its 



134 SPECIAL ANATOjMY OF THE SKELETON 

malar process; behind, by the posterior border of the external pterygoid plate and 
the emiiientia articularis; above, by the pterygoid ridge on the outer surface of the 
greater wing of the sphenoid and the under part of the squamous portion of the 
temporal ; below, by the alveolar border of the maxilla ; internally, by the external 
pterygoid plate; and externally, by the zygomatic arch and ramus of the mandible 
(Fig. 100). It contains the lower part of the Temporal, the External and Internal 
pterygoid muscles, the internal maxillary artery and vein, and inferior maxillary 
nerve and their branches. In its roof are seen the foramen ovale and the foramen 
spinosum; on its anterior wall open the posterior dental canals. At its upper and 
inner part may be observed the sphenomaxillary and pterygomaxillary fissures. 

The sphenomaxillary fissure {fissura orbitalis inferior), horizontal in direction, 
opens into the outer and back part of the orbit. It is formed above bj' the lower 
border of the orbital surface of the greater wing of the sphenoid; below, by the 
external border of the orbital surface of the maxilla and a small part of the palate 
bone; externally, by a small part of the malar bone;^ internally, it joins at right 
angles with the pterygomaxillary fissure. This fissure permits the orbit to com- 
municate with three fossae — the temporal, zygomatic, and sphenomaxillary fossae; 
it transmits the superior maxillary nerve and its orbital branch, the infraorbital 
vessels, and ascending branches from the sphenopalatine or Meckel's ganglion. 

The pterygomaxillary fissure is vertical, and descends at right angles from the 
inner extremity of the preceding; it is a V-shaped interval formed by the diver- 
gence of the maxilla from the pterygoid process of the sphenoid. It serves 
to connect the sphenomaxillary fossa with the zygomatic fossa, and transmits 
the internal maxillary artery. 

The Sphenomaxillary Fossa (fossa pterygopalatina). — ^The sphenomaxillary fossa 
is a small, triangular space situated at the angle of junction of the sphenomaxillary 
and pterygomaxillary fissures, and placed beneath the apex of the orbit. It is formed 
above by the under surface of the body of the sphenoid and by the orbital process of 
the palate bone; in front, by the maxilla; behind, by the anterior surface of the base 
of the pterygoid process and lower part of the anterior surface of the greater wing of 
the sphenoid ; internally, by the vertical plate of the palate. This fossa has three 
fissures terminating in it — the sphenoidal, sphenomaxillary, and pterygomaxillary; 
it communicates with the orbit by the sphenomaxillary fissure; with the nasal 
fossae by the sphenopalatine foramen, and with the zygomatic fossa by the pterygo- 
maxillary fissure. It also communicates with the cavity of the cranium, and has 
opening into it five foramina. Of these, there are three on the posterior wall — 
the foramen rotimdum above; below and internal to this, the Vidian canal; and 
still more inferiorly and internally, the pterygopalatine canal. On the inner wall 
is the sphenopalatine foramen, by which the sphenomaxillary communicates with 
the nasal fossa; and below is the superior orifice of the posterior palatine canal, 
besides occasionally the orifices of the accessory posterior palatine canals. The 
fossa contains the superior maxillary nerve and Meckel's ganglion, and the termi- 
nation of the internal maxillary artery. 

The Anterior Region of the Skull (norma frontalis). — The norma frontalis 
forms the face, is of an oval fo*'m, presents an irregular surface, and is excavated 
for the reception of two of the organs of sense, the eyes and the nose. It is bounded 
above by the glabella and margins of the orbit; below, by the prominence of the 
chin; on each side by the malar bone and interior margin of the ramus of the man- 
dible. In the median line are seen from above downward the glabella, and diverg- 
ing from it are the superciliary ridges, which indicate the situation of the frontal 
sinuses and support the eyebrow. Below the glabella is the frontonasal suture, 
the mid-point of which is termed the nasion, and below this is the arch of the nose, 

1 Occasionally the maxilla and the sphenoid articulate with each other at the anterior extremity of this fissure: 
the malar is then excluded from entering into its formation. 



THE SKULL AS A WHOLE 



135 



formed by the nasal bones, and the nasal processes of the maxillae. The nasal 
arch is convex from side to side, concave from above downward, presenting in the 
median line the intemasal suture (sutura inter nasalis), formed between the nasai 
bones, laterally, on either side, the nasomaxillary suture {sutura nasomaxillaris), 
formed between the nasal bone and the nasal process of the maxilla. Below the 
nose is seen the opening of the apertura pyriformis, which is heart-shaped, with 
the narrow end upward, and presents laterally the thin, sharp margins serving 
for the attachment of the lateral cartilages of the nose, and in the middle line 
below a prominent process, the anterior nasal spine, bounded by two deep notches. 
Below this is the intermaxillary suture {sutura intermaxillaris), and on each side 
of it the incisive fossa. Beneath this fossa are the alveolar processes of the maxilla 
and mandible, containing the incisor teeth, and at the lower part of the median 
line the symphysis of the chin, the mental process, with its two mental tubercles, 
separated by a median groove, and the incisive fossa of the mandible. 

On each side, proceeding from above downward, is the supraorbital ridge, 
terminating externally in the external angular process at its junction with the malar, 
and internally in the internal angular process; toward the inner third of this ridge 
is the supraorbital notch or foramen, for the passage of the supraorbital vessels 




Fig. 101. — Anterior aspect of the skull. 



and nerve. Beneath the supraorbital ridge is the opening of the orbit, bounded 
externally by the orbital ridge of the malar bone; below, by the orbital ridge 
formed by the malar and maxilla; internally, by the nasal process of the maxilla 



136 



SPECIAL ANATOMY OF THE SKELETON 



and the internal angular process of the frontal bone. On the outer side of the 
orbit is the quadrilateral outer surfact; of the malar bone, perforated by one or 
two small malar foramina. Below the inferior margin of the orbit is the infra- 
orbital foramen, the termination of the infraorbital canal, and beneath this the 
canine fossa, which gives attachment to the Levator anguli oris ; still lower are the 
alveolar processes, containing the teeth of the upper and lower jaws. Beneath the 
alveolar arch of the mandible is the mental foramen, for the passage of the mental 




\Groove for 
facial artery 



Fig. 102. — Anterolateral region of the skull. 



vessels and nerve, the external oblique line, and at the lower border of the bone, 
at the point of junction of the body with the ramus, a shallow groove for the 
passage of the facial artery. 

The Orbits. — The orbits (Fig. 102) are two quadrilateral pyramidal cavities, situ- 
ated at the upper and anterior part of the face, their bases being directed forward 
and outward, and their apices backward and inward, so that the axes of the two, if 
continued backward, would meet over the body of the sphenoid bone. Each orbit 
(orbita) is formed of seven bones — the frontal, sphenoid, ethmoid, maxilla, malar, 
lacrimal, and palate; but three of these, the frontal, ethmoid, and sphenoid, 
enter into the formation of both orbits, so that the two cavities are formed of 
eleven bones only. Each cavity presents for examination a roof, a floor, an inner 
and an outer wall, four angles, a base, and an apex. 



THE SKULL AS A WHOLE 137 

The roof {paries superior) is concave, directed downward and slightly forward, 
and formed m front by the orbital plate of the frontal; behind, by the lesser wing 
of the sphenoid. This surface presents internally the depression for the carti- 
laginous pulley of the Superior oblique muscle; externally, the depression for the 
lacrimal gland; and posteriorly, the suture connecting the frontal and lesser wing 
of the sphenoid. 

The floor (paries inferior) is directed upward and outward, and is of less extent 
than the roof; it is formed chiefly by the orbital surface of the maxilla; in front, to 
a small extent, by the orbital process of the malar, and behind, by the superior 
surface of the orbital process of the palate. This surface presents at its anterior 
and internal part, just external to the lacrimal groove, a depression for the attach- 
ment of the Inferior oblique muscle; externally, the suture between the malar 
and the maxilla; near its middle, the infraorbital groove; and posteriorly, the suture 
between the maxilla and palate bone. 

The inner or medial wall (paries medialis) is flattened, nearly vertical, and formed 
from before backward by the nasal process of the maxilla, the lacrimal, os planum 
of the ethmoid, and a small part of the body of the sphenoid. This surface pre- 
sents the lacrimal groove and crests of the lacrimal bone, and the sutures connect- 
ing the lacrimal with the maxilla, the ethmoid with the lacrimal in front, and the 
ethmoid with the sphenoid behind. 

The outer or lateral wall (paries lateralis) is directed forward and inward, and 
is formed m front by the orbital process of the malar bone; behind, bv the orljital 
surface of the greater wing of the sphenoid. On it are seen the orifices of one or 
two malar canals, and the suttn-e connecting the sphenoid and malar bones. 

Of the angles, the superior external is formed by the junction of the upper 
and outer walls; it presents from before backward, the suture connecting the 
frontal with the malar in front and with the greater wing of the sphenoid behind; 
quite posteriorly is the foramen lacerum anterius, or sphenoidal fissure, which 
transmits the third, the fourth, the three branches of the ophthalmic division of the 
trigeminal, the abducent nerve, some filaments from the cavernous plexus of the 
sympathetics, the orbital branch of the middle meningeal artery, a recurrent 
branch from the lacrimal artery to the dura, and the ophthalmic vein. The 
superior internal is formed by the junction of the upper and inner wall, and pre- 
sents the suture connecting the frontal bone with the lacrimal in front and with 
the ethmoid behind. The point of junction of the anterior border of the lacri- 
mal with the frontal has been named the dacryon. This angle presents two fora- 
mina, the anterior and posterior ethmoidal foramina, the former transmitting the 
anterior ethmoidal vessels and nasal nerve, the latter the posterior ethmoidal vessels. 
The inferior external, formed by the junction of the outer wall and floor, pre- 
sents the sphenomaxillary fissure, which transmits the superior maxillary nerve and 
its orbital branches, the infraorbital vessels, and the ascending branches from the 
sphenopalatine or Meckel's ganglion. The inferior internal is formed by the 
union of the lacrimal bone and the os planum of the ethmoid with the maxilla 
and palate bone. 

The circumference or base of the orbit, quadrilateral in form, is bounded above 
(margo supraorbitalis) by the supraorbital ridge; below (margo infraorbital is), 
by the anterior border of the orbital plate of the malar and maxilla; externally, 
by the external angular process of the frontal and malar bones ; internally, by the 
internal angular process of the frontal and the nasal process of the maxilla. The 
circumference is marked by three sutures, the frontomaxillary internally, the 
frontomalar externally, and the malomaxillary below; it contributes to the forma- 
tion of the lacrimal groove, and presents, above, the supraorbital notch (or fora- 
men), for the passage of the supraorbital vessels and nerve. 



138 SPECIAL ANA TOMY OF THE SKELETON 

The apex is situated at the back of the orbit and corresponds to the optic 
foramen,' a short circular canal which transmits the optic nerve and ophthalmic 
artery. It will thus be seen that there are nme openings communicating with 
each orbit — viz., the optic foramen, sphenoidal fissure, sphenomaxillary fissure, 
supraorbital foramen, infraorbital canal, anterior and posterior ethmoidal for- 
amina, malar foramina, and the canal for the nasal duct. 

The Nasal Cavity. — The nasal cavities {camim nasi), or nasal fossae (Figs. 81 and 
103), are two large, irregular cavities situated on either side of the middle line 
of the face, extending from the base of the cranium to the roof of the mouth, 
and separated from each other by a thin vertical septum, the septum of the nose, 
formed by the perpendicular plate of the ethmoid and by the vomer. Each 
cavity communicates by a large aperture, the anterior nasal aperture {apertura 
pyriformis),^ with the front of the face, and by the two posterior nares (choance) 




LACRIMAL CANAL PALATE BONE 

Fig. 103.— Nasal cavity, right lateral wall, from the left. (Spalteholz.) 



with the nasopharynx behind. These fosste are much narrower above than 
below, and in the middle than at the anterior or posterior openings; their depth, 
which is considerable, is much greater in the middle than at either extremity. 
The nasal fossse are surrounded by four other fossae — above is the cranial fossa; 
laterally, the orbital fossae; and below, the cavity of the mouth. Each nasal fossa 
communicates with four sinuses — the frontal above, the sphenoidal behind, and 
the maxillary and ethmoidal on the outer wall. Each fossa also communicates 
with four cavities — with the orbit by the lacrimal groove, with the mouth by the 
anterior palatine canal, with the cranium by the olfactory foramina, and with the 
sphenomaxillary fossa by the sphenopalatine foramen; and they occasionally 



iQuain, Testut, and others give the apex of the orbit aa corresponding with the inner end of the sphenoidal 
fiaaure. It seems better, however, to adopt the statement in the text, since the muscles of the eyeball take origin 
around the optic foramen, and diverge from it to the globe of the eye. 

2 In the skull freed of soft parts the anterior nasal cavities open in front by the apertura pyriformis. In the 
skull with the soft parts in place they open by the anterior nares. 



THE SKULL AS A WHOLE 139 

communicate with each other by an aperture in the septum. The bones entering 
into their formation are fourteen in number — three of the cerebral cranium, the 
frontal sphenoid, and ethmoid, and ail the bones of the face, excepting the malar 
and mandible. Each cavity is bounded by a roof, a floor, an inner and an outer 
wall. 

The upper wall, or roof, is long, narrow, and horizontal in its centre, but slopes 
downward at its anterior and posterior extremities ; it is formed in front by the 
nasal bones and nasal spine of the frontal, which are directed downward and 
forward; in the middle, by the cribriform plate of the ethmoid, which is hori- 
zontal ; and behind, by the anterior and under surface of the body of the sphenoid 
and sphenoidal turbinated process, the ala of the vomer and the sphenoidal process 
of the palate bone, which are directed downward and backward. This surface 
presents, from before backward, the internal aspect of the nasal bones ; on their outer 
side, the suture formed between the nasal bone and the nasal process of the maxilla; 
on their inner side, the elevated crest which receives the nasal spine of the frontal 
and the perpendicular plate of the ethmoid, and articulates with its fellow of the 
opposite side; while the surface of the bones is perforated by a few small vascular 
apertin-es, and presents the longitudinal groove for the nasal nerve; farther back 
is the transverse suture, connecting the frontal with the nasal in front, and the 
ethmoid behind, the olfactory foramina and nasal slit on the under surface of the 
criiiriform plate, and the suture lietween it and the sphenoid behind; quite pos- 
teriorly are seen the sphenoidal turbinated process, the orifice of the sphenoidal 
sinus, and the articulation of the ala of the vomer with the under surface of the 
body of the sphenoid. 

The floor (Fig. 103) is flattened from before backward, concave from side to 
side, and wider in the middle than at either extremity. It is formed in front 
by the palatal process of the maxilla ; behind, by the horizontal plate of the palate 
bone. This surface presents, from before backward, the anterior nasal spine; 
behind this, the upper orifices of the anterior palatine canal; the elevated crest 
which articulates with the vomer; and behind, the suture between the palate 
and maxilla, and the posterior nasal spine. 

The inner or medial wall, or septum (septum nasi osseum) (Fig. 105), is a thin 
vertical partition which separates the nasal fossse from each other. It is formed, 
in front, by the crest of the nasal bones and nasal spine of the frontal ; in the 
middle, by the perpendicular plate of the ethmoid and ethmoidal crest of the 
sphenoid; behind, by the vomer and rostrum of the sphenoid; below, by the crests 
of the maxillae and palate bones. It presents, in front, a large, triangular notch, 
which receives the septal cartilage of the nose; and behind, the grooved edge of the 
vomer. Its surface is marked by numerous canals for vessels and nerves, and 
the groove for the nasopalatine nerve, and is traversed by sutures connecting 
the bones of which it is formed. 

The outer or lateral wall (Figs. 81 and 103) is formed, in front, by the nasal 
process of the maxilla and lacrimal bones ; in the middle, by the ethmoid and inner 
surface of the body of the maxilla and turbinated bone; behind, by the vertical 
plate of the palate bone; and the internal pterygoid plate of the sphenoid. Upon 
this outer wall are two marked projections of bone (Fig. 81). One is known 
as the turbinated bone and the other as the middle turbinated process. The supe- 
rior turbinated process appears as a less distinct bony projection. This surface 
presents three irregular longitudinal passages, termed the superior, middle, and 
inferior meatuses of the nose (Fig. 104). The superior meatus, the smallest of 
the three, is situated at the upper and back part of each nasal fossa, occupying 
the posterior.third of the outer wall. It is situated between the superior and mid- 
dle turbinated processes, and has opening into it two foramina, the sphenopalatine 
foramen at the back of its outer wall, and the posterior ethmoidal cells at the front 



140 



SPECIAL ANATOMY OF THE SKELETON 



part of the outer wall. The sphenoidal sinus opens into a recess (recesstw spheno- 
ethmoidalis) , which is situated above and behind the superior turbinated process. 
The middle meatus is situated external to the middle turbinated process, between 



TRUM OF-iJ 




STLE PASSED THRG 
NDIBULUM FROM 
TAL SINUS TO 
LE MEATUS 



OBE PASSED 
THROUGH LACRI- 
L CANAL 



NTAL CANAL 



ASAL CANAL 



Fig. 104. — Coronal section through the frontal sinus and nasal fossa. (Poirier and Charpy.) 



Crest of nasal bone. 

Nasal spine of 
frontal boi 



Space for triangula) 
cartilage of ieptiini 




» . " Ci est of palate bone. 
Crest of maxilla. 



Fig. 105. — Inner wall of nasal fossEe, or septum of i 



THE SKULL AS A WHOLE 



141 



it and the turbinated bone, and extends from the anterior end of the turbinated 
to the sphenopalatine foramen of the outer wall of the nasal fossa. Anteriorly 
it terminates in a depression, the atrium of the nasal meatus {atrium meatiw medii). 
The middle meatus presents in front the orifice of the infundibulimi, by which 
the middle meatus communicates with the anterior ethmoidal cells, and through 
these with the frontal sinuses. The posterior ethmoidal cells also open into 
this meatus, while at the centre of the outer wall is the orifice of the maxillary 
antrum which varies somewhat as to its exact position in different skulls. The 
inferior meatus, the largest of the three, is the space between the turbinated bone 
and the floor of the nasal fossa. It extends along the entire length of the outer 
wall of the nose, is broader in front than behind, and presents anteriorly the lower 
orifice of the canal for the nasal duct. 



Pituitary 
fossa 



Mesoderm of base 
of skull 




Development of the Skull. — Up to a cei-tain stage the development of the skull corresponds 
with that of the vertebral column; but it is modified later in association with the expansion of 
the brain vesicles, the formation of the organs of smell, sight, and hearing, and the development 
of the mouth and pharynx. 

The notochord extends as far forward in the 
base of the future skull as the anterior end of the 
mid-brain, and becomes partly surrounded by 
mesoderm (Fig. 106). The posterior part of this 
mesodermal investment corresponds with the 
future basiocciput, and shows a subdivision into 
four segments, which are separated by the roots 
of the hypoglossal nerve. The mesoderm then 
extends over the brain vesicles, and thus the entire 
brain is enclosed by a mesodermal investment, 
which is termed the membranous primordial cra- 
nium. From the inner layer of this the bones of 
the skull and the membranes of the brain are de- 
veloped; from the outer layer the muscles, blood- 
vessels, true skin, and subcutaneous tissues of the 
scalp. In the shark and dog-fish this ineinbnin- 
ous cranium undergoes complete chondrifi( ation, 
and forms the cartilaginous skull, or rliondro- 
cranium, of these animals. In mammals, on the 
other hand, the process of chondrification is 
limited to the base of the skull — the roof and 
sides being covered in by membrane. Thus, 
the bones of the base of the skull are preceded 

by cartilage, those of the roof and sides by membrane. The posterior part of the base of the 
skull is developed around the notochord, and exhibits a segmented condition analogous to 
that of the vertebral column, while the anterior part arises in front of the notochord and shows 
no regular segmentation. The base of the skull may therefore be divided into (a) o chordal or 
vertebral, and (6) a prechordal or prevertebral portion. 

In the lower vertebrates two pairs of cartilages are developed, viz., a pair of parachordal 
cartilages, one on either side of the notochord; and a pair of prechordal cartilages, the trabeculae 
cranii, in front of the notochord (Figs. 107 and 108). The parachordal cartilages (Fig. 108) unite 
to form a cartilaginous plate, from which the cartilaginous part of the occipital bone and the basi- 
sphenoid are developed. On the lateral aspect of the parachordal cartilages the otic or auditory 
■vesicles are situated, and the mesoderm enclosing them is soon converted into cartilage, forming 
the cartilaginous ear capsules. These cartilaginous ear capsules, which are of an oval shape, 
fuse with the lateral aspects of the basilar plate, and from them arise the petromastoid portions 
of the temporal bones. The trabeculae cranii (Fig. 107) are two curved bars of cartilage which 
embrace the pituitary body; their posterior ends soon unite with the basilar plate, while their 
anterior ends join to form the ethmoidal plate, which extends forward between the forebrain and 
the olfactory pits. Later, the trabecula; meet and fuse below the pituitary body, forming the 
floor of the pituitary fossa, and so cutting off the anterior lobe of the pituitary body from the stoma- 
todeum. The mesal part of the ethmoidal plate forms the bony and cartilaginous parts of the 
nasal septum. From the lateral margins of the trabeculae cranii three processes grow out on 
either side. The anterior forms the lateral mass of the ethmoid and the alar cartilages of the 
nose; the middle gives rise to the lesser wing of the sphenoid, while from the posterior the greater 
wing and external pterygoid plate of the sphenoid are developed (Figs. 109 and 110). The bones 



Anterior arch of atlas 

Notochord 

Body of axis 

Third cervical 
vertebra 

Fig, 106. — Sagittal section of cephalic end of 
notochord. (Furness). 



142 



SPECIAL ANATOMY OF THE SKELETON 



of the vault are of membranous formation, and are termed dermal or covering hones. They are 
partly developed from the mesoderm of the primordial cranium, and partly from that which 
lies outside the entoderm of the foregut. They comprise the upper part of the tabular por- 
tion of the occipital (interparietal), the squamous temporals and tympanic plates, the panetals, 



Situation of olfactory pit Ethmoid plate 

and nasal Olfactory organ 
K sp.ptu 



Pituitary fossa 



Extension around 
olfactory organ 
Foramina for 
olfactory nerves 

— Eyehall 
-- Pituitary fossa 




Figs. 107 and 108. — Diagrams of the cartilaginous cranium. (Wiedersheim.) 




Meckel's cartilage 
Malleus 
Incus 

Int. aud. meat 
JugutXar f '>*>■' >*''' ■ 

Fossa sub' « ' 



^--^^&rya 



Optic foramen. 
^ r^!& Greater wing of 




Eor. hypi 



Foramen magnum. 

Fig. I09.-Model of the chondrocranium of .a^human embryo. 8'^f„., The membrane bones are not 
represented. (From Hertwig's Handbuch der Entwickelungslehre.) 

the frontal the vomer, the internal pterygoid plates, and the bones of the face. Some of them 

remain diiinct throughout life (.. i parietal and frontal), while others 30m w>th the bones of 

thrchondrocrani^m (.. q.. interparietal, squamous temporals, arid internal pterygoid plate ). 

Recent Ob ervations have shown that, in mammals, the basicranial cartilage, both m the 



THE SKULL AS A WHOLE 



143 



chordal and prechordal regions of the base of the skull, is developed as a single plate, which 
extends from behind forward. In man, however, its posterior part shows an indication of its 
being developed from two chondrifying centres which fuse rapidly in front and below. The 
relation of this cartilaginous plate to the notochord differs in different animals. In the ral embryo 
it lies vcntrad of the notochord (Robinson); in the sheep, pig, calf, and ferret the cranial |i;irl of 
the notochord is enclosed within it; in man, the anterior and posterior thirds of (he carlilage 
surround the notochord, but its middle third lies on the dorsal aspect of the notochord, which in 
this region is placed between the cartilage and the wall of the pharynx. 



Optic foramen 



g of sphenoid 



Nasal capsule 



Nasal septu: 




Maxilla. 

Vomer 



Meckel s cartilage f^ ^^ / j \ i>tt/hid process 

Thyroid carlilagc'-^^^^^fj^lf^lJ Fen. cocldeae. 
Cricoid cartilage. ^^ For. h'jpogl. 

Fig. 110. — The same model as shown in Fig. 109 from the left side. Certain of the membrane bones of the 
right side are represented in yellow. 

Differences in the Skull Due to Age. — At birth the skull as a whole is large in pro- 
portion to the other parts of the skeleton, but its facial portion is small, and equals only about 
one-eighth of the bulk of the cranium as compared with one-half in the adult. The frontal and 
parietal eminences are prominent, and the greatest width of the skull is at the level of the latter; 
on the other hand, the glabella, superciliary ridges, and mastoid processes are not developed. 
Ossification of the skull bones is not completed, and many of them — e. g., the occipital, 
temporals, sphenoid, frontal, and mandible — consist of more than one piece. Unossified 





^ . , Fig 112, — The lateral fontanelles. 

Fig. hi, — Skull at birth, showing the anterior 
and posterior fontanelles. 

membranous intervals, termed /o.ta.Wfes-, are seen at ^e angles of the parietal bones; th^ 

"The a,aerior or hreg.naiic fonianelle (Fig. Ill) is the largest, an A is ^^^ j^Z 
of the sagittal, coronal, and interfrontal sutures; U ,s '-^"g^-^J.^^'^^^'^i^J^^X V- -■"•"^ 
inch and a half in its antero-posterior and an mch in its transNerse diametei, / 



144 SPECIAL ANATOMY OF THE SKELETON 

fontanelle is triangular in form and is situated at the junction of the sagittal and lambdoid sutures. 
The \?ittT?A fontanelles (Fig. 112) are small, irregular in shape, and correspond respectively with 
the antero-inferior and postero-inferior angles of the parietal bones. An additional fontanelle 
is sometimes seen in the sagittal suture at the region of the obelion. The fontanelles are usually 
closed by the growth and extension of the bones which surround them, but sometimes they are 
the sites of separate ossific centres which develop into Wormian bones. The posterior and 
lateral fontanelles are obliterated within a month or two after birth, but the anterior is not com- 
pletely closed until the first half of the second year; sometimes it remains open beyond the second 
year, a condition which is usually seen in rhachitis, and is due to malnutrition. A knowledge of 
the shape and position of the fontanelles is of service to the accoucheur in enabling him to deter- 
mine which part of the fetal head is presenting during parturition. 

The small size of the face at birth is mainly accounted for by the rudimentary condition of the 
ja\\»s, the noneruption of the teeth, and the small size of the maxillary air sinuses and nasal 
cavities. At birth the nasal cavities lie almost entirely between the orbits, and the lower border 
of the anterior nasal aperture is only a little below the level of the orbital floor. With the eru]3- 
tion of the milk teeth there is an enlargement of the face and jaws, and these changes are still 
more marked after the second dentition. 

The skull grows rapidly from birth to the seventh year, by which time the foramen magnum 
and petrous parts of the temporals have reached their full size and the orbital cavities are only 
a little smaller than those of the adult. Growth is slow from the seventh year until the approach 
of puberty, when a second period of activity takes place; this consists of an increase in all direc- 
tions, but it is especially marked in the frontal and facial regions, where it is associated with the 
development of the air sinuses. 

Obliteration of the Sutures.. — Obliteration of the sutures of the vault takes place as age 
advances, usually beginning during the fourth decade of life and first becoming manifest on the 
inner surface, appearing externally about ten years later; the posterior part of the sagittal suture 
is usually the first to become obliterated, next the coronal, and then the lambdoid. The most 
striking feature of an old skull is the marked diminution in the size of the jaws consequent on 
the loss of the teeth and the absorption of the alveolar processes, thus reducing the facial height 
and altering the mandibular angles. 

Differences in the Skull Due to Sex. — Until the age of puberty little difference exists be- 
tween the male and the female skull. The skull of an adult female is, as a rule, lighter and 
smaller. While the cranial capacity of white males averages 1560 c.c, that of females is nearly 
200 c.c. less. The female skull has thinner walls, its ridges for muscle attachment are less 
strongly marked, the superciliary ridges, glabella, and mastoid processes are less prominent, and 
the corresponding air sinuses are smaller. The upper margin of the orbit is sharper, the frontal 
and parietal eminences are more prominent, and the vault is somewhat flattened as compared 
with the male skull. The contour of the face is more rounded, the facial bones are smoother, 
and the jaws and teeth are smaller. 

No single structural characteristic, however, serves to determine the sex, and the features 
enumerated above can guide in the examination only when they are sufficiently pronounced to 
justify a probable diagnosis.' 

Supernumerary, Wormian,- Sutural, or Epactal Bones (Ossa Triquetra). 

In addition to the constant centres of ossification of the skull, additional ones are occasion- 
ally found in the course of the sutures. These form irregular, isolated bones, interposed between 
the cranial bones, and have been termed Wormian bones, or ossa triquetra. They are most 
frecjuently found in the course of the lambdoid suture, but occasionally also occupy the situation 
of the fontanelles, especially the posterior and, more rarely, the anterior. Frequently one is 
found between the anterior inferior angle of the parietal bone and the greater wing of the sphe- 
noid, the epipteric bone, or the pterion ossicle (Fig. 113). They have a great tendency to be 
symmetrical on the two sides of the skull, and they vary much in size, being in some cases not 
larger than a pin's head, and confined to the outer table; in other cases so large that one pair of 
these bones maj' form the whole of the occipital bone above the superior cmwed lines. 

Craniology. 

Skulls vary in shape and size, and the term craniology is applied to the comparative study 
of these variations. By means of exact measurements and their correlation, skulls may be 
classified in various w-ays. 

' See P. J. Mobius: Ueber die Verschiedenheit mannlicher und weiblicher Schiidel. Archiv fur Anthiopologie, 
1907, N. F., vol. vi. 

2 Wormiu3, a physician of Copenhagen, is said to have given the first detailed description of these bones. 



THE SKULL AS A WHOLE 



145 



I. According to capacity, measured by means of shot, mustard seed, etc. 

1 Microcephalic, with a capacity of less than 1350 c.c. (e. g., Australians, Andamanese). 

2. Mesocephalic, with a capacity of from 1350 to 1450 c.c. (e g., Negroes, Chinese). 

3. Megacephalic, with a capacity of over 1450 c.c. (e. g., Europeans, Japanese, and Eskimos). 




F:g. 113. — Wormian bones. 





Fig. 114. — Brachycephalic cranium. (Poirier 
and Charpy.) 



Fig. 115. — Dolichocephalic cranium (Poirier 
and Charpy.) 




Fig. 116. — Brachycephalic 

and Charpy.) 



FiG. 1)7 — Dolichocephalic cranium. (Poirier 
and Charpy.) 



146 SPECIAL ANATOMY OF THE SKELETON 

II. — To facilitate regional description and to compare the normae of one skull with those of 
another, the skull is placed in such a way that a plane passing through the inferior margin of the 
orbit and the superior margin of the external auditory meatus shall be horizontal (the horizontal 
line of the Frankfort agreement). Various linear and arc measurements are made between 
definite and easily localized points on the surface of the skull, and, although previously men- 
tioned, are here tabulated for convenience of reference. They are divided into two groups; 
(1) those in the mesal plane, and (2) those on either side of it. - 

The Points in the Mesal Plane are: 

Mental Point. — The most prominent point of the chin. 

Alveolar Point, or Prosthion. — The central point of the anterior margin of the upper alveolar 
arch. 

Subnasal Point. — The middle of the lower border of the anterior nasal aperture, at the base of 
the nasal spine. 

Nasion. — The central point of the frontonasal suture. 

Glabella. — The point in the middle line at the level of the superciliary ridges. 

Ophryon. — The point in the middle line at the level where the temporal lines most nearly 
approach each other. 

Bregma. — The meeting point of the coronal and sagittal sutures. 

Obelion. — A point in the sagittal suture on a level with the parietal foramina. 

Lambda. — The point of junction of the sagittal and lambdoid sutures. 

Occipital Point. — The point in the middle line of the occipital bone farthest from the glabella. 

Inion. — The external occipital protuberance. 

Opisthion. — The mid-point of the posterior margin of the foramen magnum. 

Basion. — The mid-point of the anterior margin of the foramen magnum. 

The Points on Either Side of the Mesal Plane are: 

Gonion. — The outer margin of the angle of the mandible. 

Dacryon. — The point of union of the antero-superior angle of the lacrimal with the frontal 
bone and the frontal process of the maxilla. 

Stephanion. — The point where the temporal line intersects the coronal suture. 

Pterion. — The point where the greater wing of the sphenoid joins the antero-inferior angle 
of the parietal. 

Auricular Point. — The centre of the orifice of the external auditory meatus. 

Asterion. — The point of meeting of the lambdoid, masto-occipital, and mastoparietal sutures. 

The horizontal circumference of the cranium is measured in a plane passing through the 
glabella (Turner) or the ophryon (Flower) in front, and the occipital point behind; it averages 
about twenty inches (50 cm.) in the female and twenty-one inches (52.5 cm.) in the male. 

The occipitofrontal or longitudinal arc is measured from the nasion over the middle line of the 
vertex to the opisthion; while the basinasal length is the distance between the basion and the 
nasion. These two measurements, plus the antero-posterior diameter of the foramen magnum, 
represent the vertical circumference of the cranium. 

The length is measured from the glabella to the occipital point, while the breadth, or greatest 

transverse diameter, is usually found near the external auditory meatus. The proportion of 

, ,, , , (breadth X 100) . , , , ,. . , 

breadth to length -. -r is termed the cephalic index, or index of breadth. 

The hei-ght is usually measured from the basion to the bregma, and the proportion of height 
, , (height X 100) 
to length j TT constitutes the vertical or height index. 

In studying the face the principal points to be noticed are the proportion of its length and 
breadth, the shape of the orbits and of the anterior nasal aperture, and the degree of projection 
of the jaws. 

The length of the face may be measured from the ophryon or nasion to the chin, or, if the man- 
dible be wanting, to the alveolar point; while its ividth is represented by the distance between the 
zygomatic arches. By comparing the length with the width of the face, skulls may be divided 
into two groups — dolichofacial, or leptoprosope (long-faced), and brachyfadal, or chemoprosnpe 
(short-faced). 

The orbital index signifies the proportion which the orbital height bears to the orbital width, 
thus: 

orbital height X 100 
orbital width 

The na-sal index expresses the proportion which the width of the anterior nasal aperture bears 
to the height of the nose, the latter being measured from the nasion to the lower margin of the 
nasal aperture, thus: 

nasal width X 100 
nasal height 



THE SKULL Afi A WHOLE 



147 



The degree of projection of the jaws is determined by the fjiiathic or alveolar index, which 
represents the proportion between the basialveolar and basinasal lengths, thus: 

basialveolar length X 100 
basinasal length 

The following table, modified from that given by Duckworth, illustrates how these different 
indices may be utilized in the classification of skulls. 



Index. 


Classification. 


Nomenclature. 


Examples. 


1. Cephalic . 


Below 75 

Between 75 and SO 

Above 80 


Dolichocephalic 
Mesaticephalic 
Brachycephalic 


Kaffirs and Native Australians 
Europeans and Chinese 
MongoUans and Andamans 


2. Orbital . . 


Below 84 

Between 84 and 89 

Above 89 


Microseme 
Mesoseme 
Megaseme 


Tasmanians and Nati\'e Australians 

Europeans 

Chinese and Polynesians 


3. Nasal . . . 


Below 48 

Between 48 and 53 

Above 53 


Leptorhine 
Mesorhine 
Platyrhine 


Europeans 

Chinese and Japanese 

Negroes and Native Australians 


4. Gnathic . 


Below 98 

Between 98 and 103 

Above 103 


Orthognathous 
Mesognathous 
Prognathous 


Europeans 

Chinese and Japanese 

Native Australians 



Surface Form. — The various bony prominences or landmarks which can be easily felt and 
recognized in the head and face, and which afford the means of mapping out the important struc- 
tures comprised in this region, are as follows: 



1. Supraorbital arch. 

2. Internal angular process. 

3. E.xternal angular process. 

4. Zygomatic arch. 

5. Mastoid process. 

6. External occipital protuberance. 

7. Superior curved line of occipital bone. 



8. Parietal eminences. 

9. Temporal ridge. 

10. Frontal eminences. 

1 1 . Superciliary ridges. 

12. Nasal bones. 

13. Lower margin of orbit. 

14. Mandible. 



(1) The supraorbital arches are to be felt throughout their entire extent, covered by the eye- 
brows. They form the upper boundary of the circumference or base of the orbits, and separate 
the face from the forehead. They are strong and arched, and terminate internally on each side 
of the root of the nose in the internal angular process, which articulates with the lacrimal bone. 
Externally they terminate in the external angular process, which articulates with the malar bone. 
This arched ridge is sharper and more defined in its outer than in its inner half, and forms an 
overhanging process which protects and shields the lacrimal gland. It thus protects the eye in 
its most exposed situation and in the direction from which blows are most likely to descend. ' The 
supraorbital arch varies in prominence in different individuals. It is more marked in the male 
than in the female, and in some races of mankind than others. In the less civilized races, as the 
forehead recedes backward, the supraorbital arch becomes more prominent, and approaches 
more to the characters of the monkey tribe, in which the supraorbital arches are very largely devel- 
oped, and acquire additional prominence from the oblique direction of the frontal bone. (2) The 
internal angular process is scarcely to be felt. Its position is indicated by the angle formed 
by the supraorbital arch with the nasal process of the maxilla and the lacrimal bone at the inner 
side of the orbit. Between the internal angular processes of the two sides is a broad surface 
which as.sists in furiiiiiig the root of the nose, and immediately above this a broad, smooth, 
somewhat ti-iaiiguhir suifiicc, the glabella, situated between the superciliary ridges. (3) The 
external angular process is much more strongly marked than the internal, and is plainly to be 
felt. It is formed by the junction or confluence of the supraorbital and temporal ridges, and, 
articulating with the malar bone, it serves to a very considerable extent to support the bones of 
the face. In carnivorous animals the external angular process does not articulate with the malar, 
and therefore this lateral support to the bones of the face is not present. (4) The zygomatic 
arch is plainly to be felt throughout its entire length, being situated almost immediately under 
tne skin. It is formed by the malar bone and the zygomatic process of the temporal bone. At 
its anterior extremity, where it is formed by the malar bone, it is broad arjfl forms the prominence 



148 SPECIAL ANATOMY OF THE SKELETON 

of the cheek; the posterior part is narrower, and terminates just in front and a little above the 
tragus of the external ear. "I'he lower border is more plainly to be felt than the upper, in conse- 
quence of the dense temporal fascia being attached to the latter, which somewhat obscures its 
outline. Its shape differs very much in individuals and in different races of mankind. In the 
skulls of savages — as, for instance, in the skull of the negro of the Guinea Coast — the malar bones 
project forward and not outward, and the zygoma at its posterior extremity extends farther 
outward before it is twisted on itself to be prolonged forward. This makes the zygomatic arch 
stand out in bold relief, and affords greater space for the Temporal muscle. In skulls which 
have a more pyramidal shape, as in the Eskimos or Greenlanders, the malar bones do not pro- 
ject forward and downward under the eyes, as in the preceding form, but take a direction out- 
ward, forming with the zygoma a large, rounded sweep or segment of a circle. Thus it happens 
that if two lines are drawn from the zygomatic arches, touching the temporal ridges, they meet 
above the top of the head, instead of being parallel, or nearly so, as in the European skull, in 
which the zygomatic arches are not nearly so prominent. This gives to the face a more or less 
oval type. (5) Behind the ear is the mastoid portion of the temporal bone, plainly to be felt, 
and terminating below in a nipple-shaped process. Its anterior border can be traced immediately 
behind the concha, and its apex is on about a level with the lobule of the ear. It is rudimentary 
in infancy, but gradually develops in childhood, and is more marked in the negro than in the 
European. (6) The external occipital protuberance (inion) is always plainly to be felt just 
at the level where the skin of the neck joins that of the head. At this point the skull is thick for 
the purposes of safety, while radiating from it are numerous curved arches or buttresses of bone 
which give to this portion of the skull further security. (7) Running outward on either side from 
the external occipital protuberance is an arched ridge of bone, which can be more or less plainly 
perceived. This is the superior curved line of the occipital bone, and gives attachment to 
some of the muscles which keep the head erect on the vertebral column; accordingly, we find it 
more developed in the negro tribes, in whom the jaws are much more massive, and therefore 
require stronger muscles to prevent their extra weight carrying the head forward. Below this 
line the surface of bone at the back of the head is obscured by the overlying muscles. Above it 
the vault of the cranium is thinly covered with soft structures, so that the form of this part of the 
head is almost exactly that of the upper portion of the occipital, the parietal, and the frontal 
bones themselves; and in bald persons, even the lines of junction of the bones, especially the 
junction of the occipital and parietal at the lambdoid suture, may be defined as a slight depression 
caused by the thickening of the borders of the bones in this situation. (8) In the line of the 
greatest transverse diameter of the head, on each side of the middle line, are generally to be found 
the parietal eminences, one on each side of the middle line, though sometimes these eminences 
are not situated at the point of the greatest transverse diameter, which is at some other prominent 
part of the parietal region. They denote the point where ossification of the parietal bone began. 
They are much more prominent and well marked in early life, in consequence of the sharper 
curve of the bone at this period, so that it describes the segment of a smaller circle. Later in life, 
as the bone grows, the curve spreads out and forms the segment of a larger circle, so that the 
eminence becomes less distinguishable. In consequence of this sharp curve of the bone in early 
life, the whole of the vault of the skull has a squarer shape than it has in later life, and this appear- 
ance may persist in those suffering from rhachitis. The eminence is more apparent in the negro's 
skull than in that of the European. This is due to greater flattening of the temporal fossa in the 
former skull to accommodate the larger Temporal muscle which exists in these races. The 
parietal eminence is particularly exposed to injury from blows or falls on the head, but fracture 
is to a certain extent prevented by the shape of the bone, which forms an arch, so that the force 
of the blow is diffused over the bone in every direction. (9) At the side of the head may be felt 
the temporal ridge. Commencing at the external angular process, it may be felt as a curved 
ridge, passing upward and then curving backward, on the frontal bone, separating the forehead 
from the temporal fossa. It may then be traced passing backward in a curved direction, over 
the parietal bone, and, though less marked, still generally to be recognized. Finally, the ridge 
curves downward, and terminates in the posterior root of the zygoma, which separates the 
squamous from the subcutaneous mastoid portion of the temporal bone. (10) The frontal 
eminences vary a good deal in different individuals, being considerably more prominent in some 
than in others, and they are often not symmetrical on the two sides of the bodj', the one being 
much more pronounced than the other. This is often especially noticeable in the skull of the 
young child or infant, and becomes less marked as age advances. The prominence of the 
frontal eminences depends more upon the general shape of the whole bone than upon the size 
of the protuberances themselves. As the skull is more highly developed in consequence of in- 
creased intellectual capacity, so the frontal bone becomes more upright and the frontal eminences 
stand out in bolder relief. Thus they may be considered as affording, to a certain extent, an 
indication of the development of the hemispheres of the cerebrum beneath, and of the mental 
powers of the individual. They are not so much exposed to injury as the parietal eminences. 
In falls forward the upper extremities are involuntarily thrown out, and break the force of the 
fall, and tlius shield the frontal bone from injury. (11) Below the frontal eminences on the fore- 



THE 8KULL AS A WHOLE 149 

head are the superciliary ridges, which denote the position of the frontal sinuses, and vary 
according to the size of the sinuses in different individuals, being, as a rule, small in the female, 
absent in children, and sometimes unusually prominent in the male, when the frontal sinuses are 
largely developed. They commence on either side of the glabella, and a( first present a rounded 
form, which gradually fades away at their outer ends. (12) The nasal bones form the promi- 
nence of the nose. They vary much in size and shape, and to them arc due the variations in 
contour of this organ and much of the character of the face. Thus, in the Mongolian or Ethio- 
pian they are flat, broad, and thick at their base, giving to these races the flattened nose by which 
they are characterized, and differing very decidedly from the Caucasian, in whom the nose, owing 
to the shape of the nasal bones, is narrow, elevated at the bridge, and elongated downward. 
Below, the nasal bones are thin and connected with .the cartilages of the nose, and the angle or 
arch formed by their union serves to throw out the bridge of the nose, and is nuuh more marked 
in some individuals than others. (13) The lower margin of the orbit, formed by the maxilla 
and the malar bone, is plainly to be felt throughout its entire length. It is continuous inter- 
nally with the nasal process of the maxilla, which forms the inner boundary of the orbit. At the 
point of junction of the lower margin of the orbit with the nasal process is to be felt a little tubercle 
of bone, which can be plainly perceived by running the finger along the bone in this situation. 
This tubercle serves as a guide to the position of the lacrimal sac, which is situated above and 
behind it. (14) The outline of the mandible may be felt throughout its entire length. Just in 
front of the tragus of the external ear, and below the zygomatic arch, the condyle can be made 
out. When the mouth is opened this prominence of bone can be perceived advancing out of the 
glenoid fossa on to the eminentia articularis, and receding again when the mouth is closed. 
From the condyle the posterior border of the ramus can be felt extending down to the angle. 
A line drawn from the condyle to the angle would indicate the exact position of this border. From 
the angle to the symphysis of the chin the lower, rounded border of the body of the bone may be 
plainly felt. At the point of junction of the two halves of the bone is a well-marked triangular 
eminence, the mental process, which forms the prominence of the chin. 

Applied Anatomy. — The thickness of the skull varies greatly in different regions of the same 
• skull and in different individuals. The average thickness of the skullcap is about one-fifth 
of an inch (-5 mm.). The thickest portions are the occipital protuberance, the inferior portion of 
the frontal bone, and the mastoid process. The thinnest portions are the occipital fossse, the 
squamous portion of the temporal bone, and over certain sinuses and arteries. An arrest in the 
ossifying process may give rise to deficiencies or gaps, or to fissures, which are of importance in 
a medicolegal point of view, as they are liable to be mistaken for fractures. The fissures gener- 
ally extend from the margin toward the centre of the bone, but gaps may be found in the middle 
as well as at the edges. In course of time they may become covered with a thin lamina of bone. 
Occasionally a protrusion of the brain or its membranes may take place through one of these 
gaps in an imperfectly developed skull. When the protrusion consists of membranes only, and 
is filled with cerebrospinal fluid, it is called a meningocele; when the protrusion consists of 
brain as well as membranes, it is termed an encephalocele; and when the protruded brain is a 
prolongation from one of the ventricles, and is distended by a collection of fluid from an accu- 
mulation in the ventricle, it is termed a hydrencephalocele. This latter condition is some- 
times found at the root of the nose, where a protrusion of the anterior horn of the lateral ventricle 
takes place through a deficiency of the frontonasal suture. These malformations are usually 
found in the middle line, and most frequently at the back of the head, the protrusion taking place 
through the fissures which separate the four centres of ossification from which the tabular portion 
of the occipital bone is originally developed (see page 73). They most frequently occur through 
the upper part of the vertical fissure, which is the last to ossify, but not uncommonly through the 
lower part, when the foramen magnum may be incomplete. More rarely these protrusions have 
been met with in other situations than those above mentioned, both through normal fissures, as 
the sagittal, lambdoid, and other sutures, and also through abnormal gaps and deficiencies at 
the sides, and even at the base of the skull. Force may be responsible in a young person for 
separating a suture. This accident, seldom met with even in the young, is only occasionally 
encountered in older persons. 

Fractures of the skull may be divided into those of the vault and those of the 5a.se. Frac- 
tures of the vault are usually produced by direct violence. This portion of the skull varies in 
thickness and strength in different individuals, but, as a rule, is sufficiently strong to resist a very 
considerable amount of violence without being fractured. This is due to several causes — the 
rounded shape of the head and its construction of a number of secondary elastic arches, each 
made up of a single bone; the fact that it consists of a number of bones, united at all events in 
early life by a sutural ligament, which acts as a sort of buffer and interrupts the continuity of 
any violence applied to the skull; the presence of arches or ridges, both on the inside and outside 
of the skull, which materially strengthen it; and the mobility of the head upon the vertebral 
column, which further enables it to withstand violence. The elasticity of the bones of the head 
is especially marked in the skull of the child, and this fact, together with the wide separation of 



150 SPECIAL ANATOMY OF THE SKELETON 

the individual bones from each other, and the interposition between them of other and softer 
structures render fracture of the bones of the head a very uncommon event in infants and quite 
young children; as age advances and the bones become joined, fracture is more common, though 
still less liable to occur than in the adult. Fractures of the vault may, and generally do, involve 
the whole thickness of the bone; but sometimes one table may be fractured without any corre- 
sponding injury to the other. Thus, the outer table of the skull may be splintered and driven into 
the diploe, or in the frontal or mastoid regions into the frontal or mastoid cells, without any injury 
to the internal table. And on the other hand, the internal table has been fractured, and por- 
tions of it depressed and driven inward, without any fracture of the outer table. As a rule, in 
fractures of the skull the inner table is more splintered and comminuted than the outer, and 
this is due to several causes. It is thinner and more brittle; the force of the violence as it passes 
inward becomes broken up, and is more diffused by the time it reaches the inner table; the 
bone, being in the form of an arch, bends as a whole and spreads out, and thus presses the par- 
ticles together on the convex surface of the arch — i. e., the outer table — and forces them asunder 
on the concave surface or inner table; and lastly, there is nothing firm under the inner table to 
support it and oppose the force. Fractures of the vault may be simple fissures or starred and 
comminuted fractures, and these may be depressed or elevated. These latter cases of fracture 
with elevation of the fractured portion are uncommon, and can only be produced by direct 
wound. In comminuted fracture a portion of the skull is broken into several pieces, the lines 
of fracture radiating from a centre where the chief impact of the blow was felt; if depressed, a 
fissure circumscribes the radiating line, enclosing a portion of skull. If this area is circular, it 
is termed a pond fracture, and would in all probability have been caused by a round instru- 
ment, as a blackjack or hammer; if elliptical in shape, it is termed a gutter fracture, and 
would owe its shape to the instrument which had produced it, as a poker. A fracture may take 
place along the line of an ossified or partly ossified suture. When a surgeon explores the vault 
of the skull through a wound he must not mistake a Wormian bone for a fragment produced by 
a fractiu'e. A Wormian bone which may lead to mistake is encountered at the anterior inferior 
angle of the parietal bone. 

Fractures of the base are most frequently produced by the extension of a fissure from the 
vault, as in falls on the head, where the fissure starts from the part of the vault which first struck 
the ground. Sometimes, however, they are caused by direct violence, when foreign bodies have 
been forced through the thin roof of the orbit, through the cribriform plate of the ethmoid from 
being thrust up the nose, or through the roof of the pharynx. Other cases of fracture of the base 
occur from indirect violence, as in fracture of the occipital bone from impaction of the spinal 
column against its condyles in falls on the buttocks, knees, or feet, or in cases where the glenoid 
cavity has been fractured by the violent impact of the condyle of the mandible against it from 
blows on the chin. 

The most common place for fracture of the base to occur is through the middle fossa, and 
here the fissure usually takes a fairly definite course. Starting from the point struck, which is 
generally somewhere in the neighborhood of the parietal eminence, it runs downward through the 
parietal bone and the squamous portion of the temporal bone and across the petrous portion of 
this bone, frequently traversing and implicating the internal auditory meatus, to the middle 
lacerated foramen. From this it may pass across the body of the sphenoid, through the pituitary 
fossa to the middle lacerated foramen of the other side, and may indeed travel round the whole 
cranium, so as completely to separate the anterior from the posterior part. The course of the 
fracture should be borne in mind, as it explains the symptoms to which fracture in this region may 
give rise; thus, if the fissure pass across the internal auditory meatus, injury to the facial and 
auditory nerves may result, with consequent facial paralysis and deafness; or the tubular pro- 
longation of the arachnoid around these nerves in the meatus may be torn, and thus permit of 
the escape of the cerebrospinal fluid should there be a communication between the internal ear 
and the typanum and the membrana tympani be ruptured, as is frequently the case; again, if 
the fissure passes across the pituitary fossa and the mucoperiosteum covering the under surface 
of the body of the sphenoid is torn, blood will find its way into the pharynx and be swallowed, 
and after a time vomiting of blood will result. Fractures of the anterior fossa, involving the bones 
forming the roof of the orbit and nasal fossa, are generally the results of blows on the forehead; 
but fracture of the cribriform plate of the ethmoid may be a complication of fracture of the nasal 
bone. When the fracture implicates the roof of the orbit, the blood finds its way into this cavity, 
and, travelling forward, appears as a subconjunctival ecchymosis. Subconjunctival ecchymosis 
can also be caused by fracture of the malar bone. If the roof of the nasal fossa be fractured, 
the blood escapes from the nose. In rare cases there may be also escape of cerebrospinal fluid 
from the nose where the dura and arachnoid have been torn. In fractures of the posterior fossa 
extravasation of blood takes place beneath the deep fascia, and discoloration of the skin is soon 
observed in the course of the posterior auricular artery, the discoloration first appearing in the 
skin over the tip of the mastoid process of the temporal bone (Battle's sign). Some of the 
blood which was extra vasated beneath the deep fascia approaches the surface through the open- 
ings in the deep fascia for the passage of vessels and nerves. 



THE SKULL AS A WHOLE 



151 



The bones of the skull are frequently the seat of nodes, and not uncommonly necrosis 
results from this cause, also from injury. Necrosis may involve the entire thickness of the 
skull, but is usually confined to the external table. Necrosis of the internal table alone is 
rarely met with. The bones of the skull are also sometimes the seat of sarcomatous tumors. 

The skull in rachitis is peculiar — the forehead is high, square, and projecting, and the antero- 
posterior diameter of the skull is long in relation to the transverse diameter. The bones of the 
face are small and ill-developed, and this gives the appearance of a larger head than actually 
exists. The bones of the head are often thick, expecially in the neighborhood of the sutures, 
and the anterior fontanelle is late in closing, sometimes remaining unclosed until the fourth 
year. The condition of craniotabes has by some been also believed to be the result of rachitis, 
by others is believed to be due to inherited syphilis. In all probability it is due to both. In 
these cases the bone undergoes atrophic changes in patches, so that it becomes greatly thinned 
in places, generally where there is pressure, as from the pillow or nurse's arm. It is, therefore, 
usually met with in the parietal bone and vertical plate of the occipital bone. 

In congenital syphilis deposits of porous bone are often found at the angles of the parietal bones 
and two halves of the frontal bone which bound the anterior fontanelle. These deposits are 
separated by the coronal and sagittal sutures, and give to the skull the appearance of a hot cross 
bun. They are known as Parrot's nodes, and such a skull has received the name of natifonn, 




Fia. 118. — Division of the aiastoid prottss into four tquil parts An opening in the upper anterior quadrant 
reaches the mastoid antrum into the upper posterior quadrant reaches the lateral sinus the lower anterior quad- 
rant into mastoid cells; a superficial opening into the lower posterior quadrant reaches mastoid cells; a deep open- 
ing reaches the descending limb of the lateral sinus. (A. E. bchmitt.) 



from its fancied resemblance to the buttocks. The cells of the mastoid are sometimes the seat 
of suppuration as the result of infection extending backward from the tympanic cavity. In 
such cases the antrum of the mastoid must be opened in order that the pus escape. This is 
done by applying the gouge between the posterior wall of the external auditory meatus and the 
posterior root of the zygoma. This space is called the siiprameatal^ triangle of Macewen. 

In connection with the bones of the face a common malformation is cleft palate, o^ying to 
the nonunion of the palatal processes of the maxillary or preoral arch. This cleft may involve 
the whole or only a portion of the hard palate, and usually involves the soft palate also. The 
cleft is in the middle line, except it involves the alveolus in front, when it follows the suture 
between the main portion of the bone and the premaxillary bone. Sometimes the cleft runs 
on either side of the premaxillary bone, so that this bone is quite isolated from the maxillary 
bones and hangs from the end of the vomer. In such a case the premaxillary bone usually 
contains the germs of the central incisors only. In some cases there is no premaxillary bone 
and the great gap in the lip is in the median line. Cleft palate (page 106) is usually associated 
with harelip, which, when single, is almost always on one side, corresponding to the position 
of the suture between the lateral incisor and canine tooth. Some few cases of median harelip 
have been described. In double harelip there is a cleft on each side of the middle line. 

The outlines and the height of the arch of the palate vary greatly in different persons. A 
narrow palate with a high arch is common in idiots and certain degenerates. 

The bones of the face are sometimes fractured as the result of direct violence. The two 



152 SPECIAL ANATOMY OF THE SKELETON 

most commonly broken are the nasal bone and the mandible, and of these, the latter is by far the 
most frequently fractured of all the bones of the face. Fracture of the nasal bone is for the most 
part transverse, and takes place about half an inch from the free margin. The broken portion 
may be displaced backward or more generally to one side by the force which produced the lesion, 
as there are no muscles here which can cause displacement. The malar bone is probably never 
broken alone; that is to say, unconnected with a fracture of the other bones of the face. The 
zygomatic arch is occasionally fractured, and when this occurs from direct violence, as is usually 
the case, the fragments may be displaced inward. This lesion is often attended with great diffi- 
culty or even inability to open and shut the mouth, and this has been stated to be due to the 
depressed fragments perforating the temporal muscle, but would appear rather to be caused by 
the injury done to the bony origin of the Masseter muscle. Fractures of the maxilla may vary 
much in degree, from the chipping off of a portion of the alveolar arch, to an extensive comminu- 
tion of the whole bone from severe violence, as the kick of a horse. The most common situa- 
tion for a. fracture of the mandible is in the neighborhood of the canine tooth, as at this spot the 
jaw is weakened by the deep socket for the fang of this tooth; it is next most frequently fractured 
at the angle; then at the symphysis, and finally the neck of the condyle or the coronoid process 
may be broken. Occasionally a double fracture may occur, one in either half of the bone. 
The fractiu-es are usually compound, from laceration of the mucous membrane covering the 
gums. The displacement is mainly the result of the same violence as produced the injury, but 
may be fiu-ther increased by the action of the muscles passing from the neighborhood of the sym- 
physis to the hyoid bone. 

The maxilla and mandible are both of them frequently the seat of necrosis, though the disease 
affects the latter much more frequently than the former. It may be the result of periostitis, 
from tooth irritation, injury, or the action of some specific poison, as syphilis, or from salivation 
by mercury; it not infrequently occurs in children after attacks of the exanthematous fevers, and 
a special form occurs from the action of the fumes of phosphorus in persons engaged in the 
manufacture of matches. 

Tumors attack the jaw bones not infrequently, and these may be either innocent or malig- 
nant; in the upper jaw cysts may occur in the antrum, constituting the so-called dropsy of the 
antrum ; or, again, cysts may form in either jaw in connection with the teeth — either cysts con- 
nected with the roots of fully developed teeth, the "dental cyst;" or cysts connected with imper- 
fectly developed teeth, the "dentigerous cyst." Solid innocent tumors include the fibroma, 
the chondroma, and the osteoma. Of malignant tumors there are the endotheliomata, the 
sarcomata, and the epitheliomata. The sarcomata are of various kinds, the spindle-celled, 
the round-celled, which are of a very malignant character, and the myeloid sarcomata, prin- 
cipally affecting the alveolar margin of the bone. Of the epitheliomata we find the squamous 
variety spreading to the bone from the palate or gum, and the cylindrical epithelioma origi- 
nating in the antrum or nasal fossEe. 

Both mandible and maxilla occasionally recjuire excision for tumors and in some other condi- 
tions. The maxilla is removed by an incision from the inner canthus of the eye, along the side 
of the nose, around the ala, and down the middle line of the upper lip. A second incision is 
carried outward from the inner canthus of the line along the lower margin of the orbit as far as 
the prominence of the malar bone. The flap thus formed is reflected outward and the surface of 
the bone exposed, and the central incisor of the diseased side is removed. The connections 
of the bone to the other bones of the face are then divided with a narrow saw and bone-cutting 
forceps. They are (1 ) the junction with the malar bone, passing into the sphenomaxillary fissure; 
(2) the nasal process; a small portion of its upper extremity, connected with the nasal bone in 
front, the lacrimal bone behind, and the frontal bone above, being left; (3) the connection with 
the bone on the opposite side and the palate in the roof of the mouth. The bone is now firmly 
grasped with lion-jaw forceps, and by means of a rocking movement upward and downward the 
remaining attachments of the orbital plate with the ethmoid and the back of the bone with the 
palate, broken through. The soft palate is first separated from the hard with a scalpel, and is not 
removed. Occasionally in removing the maxilla it will be found that the orbital plate can be 
spared, and this should always be done if possible. A horizontal saw-cut is to be made just 
below the infraorbital foramen and the bone cut through with a chisel and mallet. Lockwood 
has pointed out that in removing the maxilla the surgeon must be careful in dividing the nasal 
process of the maxilla to preserve the internal orbital or palpebral ligament (Tendo oculi), 
because this ligament arises from the palpebral fascia, and if it is interfered with the eye will 
inevitably drop downward. Removal of one-half of the mandible is sometimes required. If 
possible, the section of the bone should be made to one side of the symphysis, so as to save the 
genial tubercles and the origin of the Geniohyoglossus muscle, as otherwise the tongue tends to 
fall backward and may produce sufl^ocation. Having extracted the central or preferably the 
lateral incisor tooth, a vertical incision is made down to the bone, commencing at the free margin 
of the lip, and carried to the lower border of the bone; it is then carried along its lower border to 
the angle and up the posterior margin of the ramus to a level with the lobule of the ear. The flap 



THE II VOID OB LINGUAL BONE 



153 



thus formed is raised by separating; all the structures attached to the outer surface of the l)one. 
The jaw is now sawed through at the point where the tooth has been extracted, and the knife 
passed along the inner side of the mandible, separating the structures attached to this surface. 
The mandible is then grasped by the surgeon and strongly depressed, so as to bring down the 
coronoid process and enable the operator to sever the tendon of the Temporal muscle. The 
mandible can be now further depressed, care being taken to not evert it nor rotate it outward, 
which would endanger the internal maxillary artery, and the External pterygoid muscle is torn 
through or divided. The capsular ligament is now opened in front and the lateral ligaments 
divided, and the mandible removed with a few final touches of the knife. 

The antrum of Highmore occasionally requires tapping for suppuration. This may be done 
through the socket of a tooth, preferably the first molar, the fangs of which are most intimately 
connected with the antrum, or through the facial aspect of the bone above the alveolar pro- 
cess. This latter method does not perhaps afford such efficient drainage, but there is less 
chance of food finding its way into the cavity. The operation may be performed by incising the 
mucous membrane above the second molar tooth, and driving a trocar or any sharp-pointed 
instrument into the cavity. 



THE HYOID OR LINGUAL BONE (OS HYOIDEUM). 

The hyoid bone (Fig. 119) is a bony arch, shaped like a horseshoe, and consist- 
ing of five segments — a body, two greater cornua, and two lesser cornua. It 
is suspended from the tips of the styloid processes of the temporal bones by 
ligamentous bands, the stylohyoid ligaments. 

The Body, or basihyal {corpus ossei hyoidei), forms the central part of the 
bone, and is of a quadrilateral form. 

Surfaces. — Its anterior surface (Fig. 119), convex, directed forward and upward, 
is divided into two parts by a vertical ridge which descends along the median 




Fia. H9. — Hyoid bone. Anterior 



line and is crossed at right angles by a horizontal ridge, so that this surface 
is divided into four spaces or depressions. At the point of meeting of these two 
lines is a prominent elevation, the tubercle. The anterior surface gives attach- 
ment to the Geniohyoid in the greater part of its extent; above, to the Genio- 
hyoglossus; belotv, to the Mylohyoid, Stylohyoid, and the aponeurosis of the 
Digastric (suprahyoid aponeurosis); and between these to part of the Hyo- 
glossus. The posterior surface is smooth, concave, directed backward and 
downward, and separated from the epiglottis by the thyrohyoid membrane 
and by a quantity of loose areolar tissue. The lateral surfaces are joined to the 
greater cornua. In early life they are connected with the cornua by cartilaginous 
surfaces, and held together by ligaments, and occasionally a synovial membrane 
is found between them. 



154 SPECIAL ANATOMY OF THE SKELETON 

Borders. — The superior border is rounded, and gives attachment to the thyro- 
hyoid membrane, part of the Geniohyoglossi and Chondroglossi muscles. The 
inferior border gives attachment, in front, to the Sternohyoid; behind, to the Omo- 
hyoid and to the part of the Thyrohyoid at its junction with the great cornua. 
It also gives attachment to the Levator glandulae thyroideae when this muscle 
is present. 

The Greater Cornua (cornua viajora), or thyrohyals, project backward from 
the lateral surfaces of the body; they are flattened from above downward, 
diminish in size from before backward, and terminate posteriorly in a tubercle 
for the attachment of the lateral thyrohyoid ligament. The outer surface gives 
attachment to the Hyoglossus, their upper border to the Middle constrictor of 
the pharynx, their lower border to part of the Thyrohyoid muscle. 

The Lesser Cornua (cornua minora), or ceratohyals, are two small, conical- 
shaped eminences attached by their bases to the angles of junction between the 
body and greater cornua, and giving attachment by their apices to the stylohyoid 
ligaments.' The smaller cornua are connected to the body of the bone by a 
distinct diarthrodial joint, which usually persists throughout life, but occasion- 
ally becomes ankylosed. 

Development. — From six centres — two (sometimes one) for the body, and one for each 
cornu. Ossification commences in the body about the eighth month, and in the greater cornua 
toward the end of fetal Ufe. Ossification of the lesser cornua commences in the first or second 
year after birth. 

Attachment of Muscles. — Sternohyoid, Thyrohyoid, Omohyoid, aponeurosis of the 
Digastric, Stylohyoid, Mylohyoid, Geniohyoid, Geniohyoglossus, Chondroglossus, Hyoglossus, 
Middle constrictor of the pharynx, and occasionally a few fibres of the Inferior lingualis. It 
also gives attachment to the thyrohyoidean membrane and the stylohyoid, thyrohyoid, and 
hyoepiglottic ligaments. 

Surface Form. — The hyoid bone can be felt in the receding angle below the chin, and the 
finger can be carried along the whole length of the bone to the greater cornu, which is situated 
just below the angle of the mandible. This process of bone is best perceived by making pressure 
on one cornu, and so pushing the bone over to the opposite side, when the cornu of this side will 
be distinctly felt immediately beneath the skin. This process of bone is an important landmark 
in ligation of the lingual artery. 

Applied Anatomy. — The hyoid bone is occasionally fractured, generally from direct vio- 
lence, as in the act of garroting or throttling. It is frequently found broken in those who have 
been hanged. The greater cornu is the part of the bone most frequently broken, but sometimes 
the fracture takes place through the body of the bone. In consequence of the muscles of the 
tongue having important connections with this bone, there is great pain upon any attempt being 
made to move the tongue, as in speaking or swallowing. 



THE THORAX. 

The thorax, or chest, is an osseocartilaginous cage, the cavity of which (cavum 
thoracis) contains and protects the principal organs of respiration and circula- 
tion. It is conical in shape, being narrow above and broad below, flattened 
from before backward, and longer behind than in front. It is somewhat reni- 
form on transverse section. 

Boundaries. — The posterior surface is formed by the twelve thoracic vertebrae 
and the posterior part of the ribs. It is concave from above downward, and pre- 
sents on each side of the middle line a deep groove, the vertebral groove, in conse- 
quence of the direction backward and outward which the ribs take from their 
vertebral extremities to their angles. The anterior surface is flattened or slightly 
convex, and inclined forward from above downward. It is formed by the sternum 

1 These ligaments in many animals are distinct bones, and in man are occasionally ossified to a certain extent. 



THE THORAX 



155 



and costal cartilages. The lateral sxirfaces are convex; they are formed by the 
ribs, separated from each other by spaces. Each space is called an intercostal 
space (sfatiwm inter costale). These are eleven in number, and are occupied by 
the intercostal muscles. 



Fir'it thoracic 




Fig. 120.— The thor: 



The superior or upper aperture of the thorax, the inlet (apertura thoracis supe- 
rior), is reniform in shape, being broader from side to side than from before back- 
ward. It is formed by fhe first thoracic vertebra behind, the upper margin 
of the sternum in front, and the first rib on each side. It slopes downward 
and forward, so that the anterior boundary is on a lower level than the posterior. 
The antero-posterior diameter is about two inches (5 cm.), and the transverse 
about Jour (10 cm.). The parts which pass through the upper opening of the 
thorax are, froiri' tefore backward in or near the middle line, the Sternohyoid 
and Sternothyroid muscles, the remains of the thymus gland, the trachea, 
oesophagus, thoracic duct, the inferior thyroid veins, and the Longus colli muscle 
of each side; at the sides, the innominate artery, the left common carotid, and 



156 



SPECIAL ANATOMY OF THE SKELETON 



left subclavian arteries, the internal mammary and superior intercostal arteries, 
the right and left innominate veins, the vagus, cardiac, phrenic, and sympathetic 
nerves, the anterior branch of the first thoracic nerve, and the recurrent laryngeal 
nerve of the left side. The apex of each lung, covered by the pleura, also projects 
through this aperture, a little above the margin of the first rib. 




Fig. 121. — The thorax. Dorsal view. (Spaltcholz.) 



The inferior or lower opening (apertura thoracis inferior) is formed by the 
twelfth thoracic vertebra behind, by the twelfth ribs at the sides, and in front 
by the eleventh, tenth, ninth, eighth, and seventh costal cartilages, which ascend 
on either side and form an angle, the subcostal angle (angulus infrasternalis), 
from the apex of which the ensiform cartilage projects. It is wider transversely 
than from before backward. It slopes oblicjuely downward and backward, so 
that the cavity of the thorax is much deeper behind than in front. The 
Diaphragm closes in the opening forming the floor of the thorax. 



THE STEBNU3I, OB BREAST BONE I57 

The Cavity of the Thorax (caviim thoracis). — The capacity of the cavity of the 
thorax does not correspond with its apparent size externally, because (1) the space 
enclosed by the lower ribs is occupied by some of the abdominal viscera; and (2) 
the cavity extends above the first rib into the neck. The size of the cavity of the 
thorax is constantly varying during life, with the movements of the ribs and 
Diaphragm, and with the degree of distention of the abdominal viscera. From 
the collapsed state of the lungs, as seen when the thorax is opened, in the dead 
body, it would appear as if the viscera only partly filled the cavity of the thorax, 
but during life there is no vacant space, that which is seen after death being 
filled up during life by the expanded lungs. 

In the female the thorax differs as follows from the male: (1) Its general capacity is less. (2) 
The sternum is shorter. (3) The upper margin of the sternum is on a level with the lower part 
•of the body of the third thoracic vertebra, whereas in the male it is on a level with the lower 
part of the body of the second thoracic vertebra. (4) The upper ribs are more movable, and 
so allow a greater enlargement of the upper part of the thorax than in the male. 



The Sternum, or Breast Bone. 

The sternum, or breast bone (Figs. 122 and 123), is a flat, narrow bone, situated 
in the median line of the front of the chest, and consisting, in the adult, of three 
portions. It has been likened to an ancient sword; the upper piece, representing 
the handle, is termed the manubrium sterni (presternum) ; the middle and largest 
piece, which represents the chief part of the blade, is termed the gladiolus 
(corpus sterni or mesosternum) ; and the inferior piece, which is hkened to the point 
of the sword, is termed the ensiform appendix {processus xiphoideus or meta- 
sternum). In its natural position its inclination is oblique from above down- 
ward and forward. It is slightly convex in front, concave behind, broad above, 
becoming narrowed at the point where the first and second pieces are connected, 
after which it again widens a little, and is pointed at its extremity. Its average 
length in the adult is abouL,§£.ven inches (17.5 cm.), being rather longer IiTthe 
male than in the female. At the junction of the manubrium and gladiolus is a 
distinct angle {angulus Ludovici), the gladiolus looking forward, the manubrium 
also looking forward, but to a less degree. This angle is on a level with the 
second rib, and is produced by retraction of the upper portion of the thorax. 

First Piece. — The manubrium sterni is of a somewhat triangular form, broad and 
thick above, narrow below at its junction with the middle piece. 

Surfaces. — Its anterior surface, convex from side to side, concave from above 
downward, is smooth, and affords attachment on each side to the Pectoralis 
major and sternal origin of the Sternomastoid muscle. In well-marked bones 
the ridges limiting the attachment of these muscles are very distinct. Its posterior 
surface, concave and smooth, affords attachment on each side of the Sternohyoid 
and Sternothyroid muscles. 

Borders. — The superior border, the thickest, presents at its centre the prestemal 
notch (i)icisura jiigularis), and on each side an oval articular surface, the 
clavicular facet (incisura clavicidaris), directed upward, backward, and outward, 
for articulation with the sternal end of the~clavicle. The inferior border presents 
an oval, rough surface, covered in the recent state with a thin layer of cartilage, 
for articulation with the second portion of the bone (synchondrosis sternalis). 
The junction of the manubrium with the gladiolus is marked by a transverse 
ridge, which corresponds to the attachment on each side of the cartilage of 
the second rib. The lateral borders are marked above by a depression (iiicisura 
cosfalis I) for the first costal cartilage, and below by a small facet, which, with a 



158 



SPECIAL ANATOMY OF THE SKELETON 




i\G. 122.— Anterior (ventral) surface of sternum and Fig. 123.— Posterior (dorsal) surface of sternum, 

costal cartilages. 



THE STERNUM, OB BREAST BONE 159 

similar facet on the upper angle of the middle portion of the bone, forms a notch 
{incisura costalis II) for the reception of the costal cartilage of the second rib. 
These articular surfaces are separated by a narrow, curved edge, which slopes 
from abo\'e downward and inward. 

Second Piece. — The gladiolus, considerably longer, narrower, and thinner than 
the first piece, is broader below than above. 

Surfaces. — Its anterior surface (planum sternale) is nearly flat, directed upward 
and forward, and marked by three transverse lines which cross the bone opposite 
the third, fourth, and fifth articular depressions. These lines are produced by the 
union of the four separate pieces of which this part of the bone consists at an early 
period of life. At the junction of the third and fourth pieces is occasionally seen 
an orifice, the sternal foramen; it varies in size and form in different individuals 
and pierces the bone from before backward. This surface affords attachment 
on each side to the sternal origin of the Fec toralis m ajor. The posterior surface, 
slightly concave, is also marked by three transverse lines, but they are less dis- 
tinct than those in front; this surface affords attachment below, on each side, 
to the Triaogul aris stern i muscle, and occasionally presents the posterior opening 
of the sternal foramen. 

Borders. — The superior border presents an oval surface for articulation with the 
manubrium. The inferior border is narrow, and articulates with the ensiform 
appendix. Each lateral border presents, at each superior angle, a small facet, 
which, with a similar facet on the manubrium, forms a cavity for the cartilage of 
the second rib; the four succeeding angular depressions receive the cartilages of 
the third, fourth, fifth, and sixth ribs; while each inferior angle presents a small 
facet, which, with a corresponding one on the ensiform appendix, forms a notch 
for the cartilage of the se\'enth rib. They are separated by a series of curved 
interarticular intervals, which diminish in length from above downward, and 
correspond to the intercostal spaces. Most of the cartilages belonging to the true 
ribs, as will be seen from the foregoing description, articulate with the sternum 
at the line of junction of two of its primitive component segments. This is 
well seen in many of the lower animals, where the separate parts of the bone 
remain ununited longer than in man. In this respect a striking analogy exists 
between the mode of connection of the ribs with the vertebral column and the 
connection of the costal cartilages with the sternum. 

Third Piece. — The ensiform or xiphoid appendix is the smallest of the three ; it 
is thin and elongated in form, cartilaginous in structure in youth, but more or 
less ossified at the upper part in the adult. 

Surfaces. — Its anterior surface affords attachment to the chondroxiphoid liga- 
ment; its posterior surface, to .some of the fibres of the Diap^liragm and Triangii^ 
laris sterni muscles; its lateral borders, to the aponeurosis of the abdominal muscles. 
Above Tf articulates with the lower end of the gladiolus, and at each superior 
angle presents a facet (incisura costalis VII), for the lower half of the cartilage 
of the seventh rib; below, by its pointed extremity, it gives attachment to the linea 
alJDa. This portion of the sternum varies much in appearance, being some- 
times pointed, broad, and thin, sometimes bifid or perforated by a circular open- 
ing, occasionally curved or deflected considerably to one or the other side. 

Structure. — The bone is composed of delicate cancellous structure, covered by a thin 
layer of compact tissue, which is thickest in the manubrium between the articular facets for 
the clavicles. 

Development. — The cartilaginous sternum originally consists of two bars, situated one on 
either side of the mesal plane and connected with the rib cartilages of its own side. It is usual 
for the eighth cartilage to lose its attachment to the sternum and become attached to the seventh 
cartilage. The sternal end of the ninth cartilage divides longitudinally, the mesal part remains 



160 



SPECIAL ANATOMY OF THE SKELETON 



attached to the sternum and becomes the ensiform process. The remaining part acquires 
attachment to the eighth cartilage. These two bars fuse with each other along the middle line, 
and the bone, including the ensiform appendix, is usually developed from six centres, one for 

the first piece or manubrium, four for the second 
piece or gladiolus, and one for the ensiform appendix. 
Up to the middle of fetal life the sternum is entirely 
cartilaginous, and when ossification takes place the 
ossific granules are deposited in the middle of the 
intervals between the articular depressions for the 
costal cartilages, iu the following order (Fig. 125): In 
the manubrium and first piece of the gladiolus, during 
the sixth month; in the second and third pieces of the 
gladiolus between the seventh and ninth months; 
the fourth piece of the gladiolus ossifies toward the 
latter part of the first year; the ensiform process 
ossifies Vjetween the fifth and eighteenth years. The 
centres appear in the upper part of each segment and 
proceed gradually downward. To these may be added 
the occasional existence, as described by Breschet, of 
two episternal centres, which make their appearance 
one on each side of the presternal notch. They 
are probably vestiges of the episternal bone of the 
monotremata and lizards. It occasionally happens 
that some of the segments are formed from more than 
one centre, the number and position of which vary (Fig. 127). Thus, the first piece may have 
two, three, or even six centres. When two are present, they are generally situated one above 
the other, the upper one being the larger;' the second piece has seldom more than one; the 




Fig. 124. — Showing ventral ends of the 
upper seven (cartilaginous) ribs fused to 
form a pair of longitudinal sternal bars. 




1 for mannbriiim 



4 for gladiobisJ^ \ 7th month 

5 1st year after birth 



'^z::^r\'''^'' ''"''""- 



[ Barely unite, 

Sijrii'" ■ '^ 1 except in old age. 




Between puberty 
and the 25th year. 



Soon after puberty. 



Partly cartilaginous to 
advanced life. 



Fig. 126. — Time of unioa of 




for first piece, two or more centres. 

12^ V""^ f<^^' second piece, usually one. 

%T~ for third 1 
'0 u tO for fourth \ 2, placed laterally. 
f^^ K) for fifth J 




Arrest of development 
of lateral pieces, producing 



Sternal fissure, and 
Sternal foramen. 



Fig, 127. — Peculiarities in number of centres of sternum. Fig. 128. — Peculiarities in mode of union of sternum. 
^ Sir George Humphry states that this is "probably the more complete condition." 



THE RIBS 101 

Non-articular pari of tubercle 
Angle I 

I 1^ Articular part of lulerclc 




third, fourth, and fifth pieces are often formed from two 
centres placed laterally, the irregular union of which will 
serve to explain the occasional occurrence of the sternal fora- 
men (Fig. 126), or of the vertical sternal fissure, which occa- 
sionally intersects this part of the bone (Fig. 126), and 
which is further explained by the manner in which the 
cartilaginous matrix, in which ossification takes place, is 
formed. Union of the various centres of the gladiolus com- 
mences about puberty, from below, and proceeds upward, 
so that by the age of twenty-five they are all united, and 
this portion of bone consists of one piece. The ensiform 
cartilage becomes joined to the gladiolus about forty. The 
manubrium is occasionally but seldom joined to the gladiolus 
in advanced life by bone. When this union takes place, 
however, it is generally only superficial, a portion of the 
centre of the sutural cartilage remaining unossified. 

Articulations. — With the clavicles and seven costal carti- 
lages on each side. 

Attachment of Muscles.— To nine pairs and one single 

muscle — the Pectoralis major, Sternomastoid, Sternohyoid, 

Sternothyroid, Triangularis sterni, aponeuroses of the 

■Shaft Obliquus externus abdominis, Obliquus internus abdominis, 

Transversalis, Rectus abdominis muscles, and Diaphragm. 



The Ribs (Costae). 

Tlie ribs are elastic arches of bone, which form 

the chief part of the thoracic wails. They are twelve 

in number on each side; but this number may be 

increased by the development of a cervical or lumbar 

rib, or may be diminished to eleven. The first^ .seven 

are connected behind with the spine and in front 

with the sternum, through the intervention of the 

costal cartilages; they are called true (vertebrosternal) 

ribs (costae verae)} The remaining five are false 

ribs {costae spuriae); of these, the first three have 

'<,\ their cartilages attached to the cartilage of the rib 

\\ ^ above, the vertebrochondral ribs; the last two are free 

V\ ^ \ ^' '^heir anterior extremities, the floating or vertebral 

\ \ \ \ ribs. The ribs vary in their direction, the upper ones 

•d l^<?'"g I^ss oblique than the lower. The extent of 

'"X ~f/ oblic{uity reaches its maximum at the ninth ril), and 

'^•^^ gradualty7recTeases~from that rib to the twelfth. The 

ribs are situated one below the other in such a 

^'^-^fdeT^rferioraipeJt.*"'"" manner that spaces are left between them. Each 

' Sometimes the eighth rib cartilage articulates with the sternum; this condition occurs more frequently on the 
■ight than on the left side. 

11 




162 



SPECIAL ANATOMY OF THE SKELETON 



space is called an intercostal space (spatium intercostale). The length of these 
spaces corresponds to the length of the ribs and their cartilages; their breadth 
is greater in front than behind, and between the upper than between the lower 
ribs. The ribs increase in length from the first to the seventh, when they again 
diminish to the twelfth. In breadth they decrease from above downward; in the 
upper ten the greatest breadth is at the sternal extremity. 

Common Characters of the Ribs. — A rib from the middle of the series 
should be taken in order to study the common characters of the ril)s (Figs. 129 
and 130). Each rib presents two extremities, a posterior or vertebral, an anterior 
or sternal, and an intervening portion — the body or shaft. 

Posterior Extremity. — The posterior or vertebral extremity presents for examina- 
tion a head, neck, and tuberosity. 

The head (capituhim costae) (Fig. 130) is marked by a kidney-shaped artic- 
ular surface, divided by a horizontal ridge (crista capituli) into two facets for 



Demifacet for vertebra 



Interariicular crest 



',C^^''%J>i|/ ^Demifacet for vertebra. 



Subcostal groove 




Fig. 130. — A central rib of the left side, viewed from bebind. 



articulation with the costal cavity formed by the junction of the bodies of two 
contiguous thoracic vertebras; the upper facet is small, the inferior one of larger 
size; the ridge separating them serves for the attachment of the interarticular 
ligament. 

The neck (collum costae) is that flattened portion of the rib which extends out- 
ward from the head; it is about an inch long, and is placedLjnJi'ont of thejracs- 
verse process of the lower of the two vertebrae with which the head articulates. 
Its anterior surface is flat and smooth, its posterior surface is rough for the attach- 
ment of the middle costotransverse ligament,^^JKt is perforated by nimierous 
foramina, the direction of which is less constant than those found on the inner 
surface of the shaft. Of its two borders, the superior border presents a rough 
crest (crista colli costae) for the attachment of the anterior costotransverse liga- 
ment; its inferior border is rounded. On the posterior surface of the neck, just 
where it joins the shaft, and nearer the lower than the upper border, is an eminence 
— the tuberosity, or tubercle. 

The tuberosity (tuhrrciilnm costae) consists of an articular and a nonanicular 
portion. The articular portion (fades articularis tubercidi costae), the more in- 
ternal and inferior of the two, presents a small, oval surface or articulation with 
the extremity of the transverse process of the lower of the two vertebrse to which 
the head is connected. The nonarticular portion is a rough elevation, which 



THE RIBS 153 

affords attachment to the posterior costotransverse ligament. The tiihercle is 
much more prominent in the upper than in tlie lower ril)s. 

Anterior Extremity. — The anterior or sternal extremity is flattened, and presents 
a porous, oval, concave depression, into which the costal cartilage is received. 

The shaft (cor-pus costae) is thin and flat, so as to present two surfaces, an 
external and an internal, and two borders, a superior and an inferior. 

The external surface is convex, smooth, and marked at its back part, a little 
in front of the tuberosity, by a prominent line, directed obliquely from above 
downward and outward; this gives attachment to a tendon of the Iliocostalis_ 
muscle or of one of its accessory portions, and is called the angle (anc/ulus costae). 
At this point the rib is bent in two directions. If the rib is laid upon its lower 
border, it will be seen that the portion of the shaft in front of the angle rests upon 
this border, while the portion of the shaft behind the angle is bent inward and at 
the same time tilted upward. The interval between the angle and the tuberosity 
increases gradually from the second to the tenth rib. The portion of bone between 
these two parts is rounded, rough, and irregular, and serves for the attachment of 
the Longissimus dorsimuscle. The portion of bone between the tubercle and 
sternal extremity is also slightly twisted upon its own axis, the external surface 
looking downward behind the angle, a little upward in front of it. This surface 
presents toward its sternal extremity an oblique line, the anterior angle. 

The internal surface is concave, smooth, directed a little upward behind the angle, 
a little downward in front of it. This surface is marked by a ridge which com- 
mences at the lower extremity of the head; it is strongly marked as far as the 
inner side of the angle, and gradually becomes lost at the junction of the anterior 
with the middle third of the bone. The interval between it and the inferior border 
presents a groove, subcostal groove {sulcus costae), for the intercostal vessels and 
nerve. At the back part of the bone this groove belongs to the inferior border, 
but just in front of the angle, where it is deepest and broadest, it corresponds to 
the internal surface. The superior edge of the groove is rounded; it serves for 
the attachment of the Internal intercostal muscle. The inferior edge corresponds 
to the lower margin of the rib and gives attachment to the External intercostal 
muscle. Within the groove are seen the orifices of numerous small foramina 
which traverse the wall of the shaft obliquely from before backward. 

The superior border, thick and rounded, is marked by an external and an inter- 
nal lip, more distinct behind than in front; they serve for the attachment of the 
External and Internal intercostal muscles. 

The inferior border, thin and sharp, has attached to it the External intercostal 
muscle. 

Peculiar Ribs. — The ribs which require especial consideration are five in 
number, viz., the first, second, tenth, eleventh, and twelfth. 

First Rib. — The first rib (Fig. 131) is the shortest and the most curved of all 
the ribs; it is broad and flat, its surfaces looking upward and downward, and 
its borders inward and outward. The head is of small size, rounded, and presents 
only a single articular facet for articulation with the body of the first thoracic ver- 
tebra. The neck is narrow and rounded. The tuberosity, thick and prominent, 
rests on the outer border. There is no angle, but in this situation the rib is slightly 
bent, with the convexity of the bend upward, so that the head of the bone is 
directed downward. The upper surface of the shaft is marked by two shallow 
depressions, separated by a small rough surface (tuberculum scaleni) for the attach- 
ment of the Scalenus anticus muscle — the shallow groove in front of it trans- 
mitting the subclavian vein, the deeper groove behind it (sulcus subclaviae^ 
the subclavian artery. Between the groove for the subclavian artery and the 
tuberosity is a rough surface, for the attachment of the Scalenus medius muscle. 
The under surface is smooth, and destitute of the groove observed on the other 



164 SPECIAL ANATOMY OF THE SKELETON 

ribs The outer border is convex, thick, and rounded, and at its posterior part 
gives attachment to the first serration of the Serratus magnus; the inner is con- 
cave thin and sharp, and marked about its centre by the commencement ot 




Bm^i^^^^'''' 



Single articular facet — 



SinjZe arftCM/rtr/ncrf.— ^^^^ Tuberosity 11 



Single articular facet. 




Figs. 131 to 135.— Pecul 



the rough surface for the Scalenus anticus. The anterior extremity is larger and 
thicker than any of the other ribs. 

Second Rib.— The second rib (Fig. 132) is much longer than the first, but bears 
a very considerable resemblance to it in the direction of its curvature. The non- 



THE COSTAL CARTILAGES 165 

articular portion of the tuberosity is occasionally only slightly marked. The angle 
is slight and situated close to the tuberosity, and the shaft is not twisted, so tliat 
both ends touch any plane surface upon which it may be laid; but there is a similar 
though slighter bend, with its convexity upward, to that found in the first rib. The 
shaft is not horizontal, like that of the first rib, its outer surface, which is convex, 
looking upward and a little outward. It presents, near the middle, a rough emi- 
nence {tuberositas costae II), for the attachment of part of the first and all of the 
second digitations of the Serratus magnus; behind and above which is attached 
the Scalenus posticus. The inner surface, smooth and concave, is directed down- 
ward and a little inward; it presents a short groove tow^ard its posterior part. 

Tenth Rib. — The tenth rib (Fig 133) has only a single articular facet on its head. 

Eleventh and Twelfth Ribs.— The eleventh and twelfth ribs (Figs. 134 and 
135) have each a single articular facet on the head, which is of rather large size; 
they have no neck or tuberosity, and are pointed at the extremity. The eleventh 
has a slight angle and a shallow groove on the lower border. The twelfth has 
neither, and is much shorter than the eleventh, and the head has a slight inclina- 
tion downward. Sometimes the twelfth rib is even shorter than the first. 

Structure. — The ribs consist of cancellous tissue enclosed in a thin layer of compact bone. 

Development. — Each rib, with the exception of the last two, is developed from three centres, 
one for the shaft near the angle, one for the head, and one for the tubercle. The last two ribs 
have only two centres, that for the tubercle being wanting. Ossification commences in the 
shaft of the ribs between the ninth and eleventh weeks before its appearance in the vertebrje. 
The epiphysis of the head, which is of slightly angular shape, and that for the tubercle, of a 
lenticular form, make their appearance between the sixteenth and twentieth years, and are not 
united to the rest of the bone until about the twenty -fifth year. 

Attachment of Muscles. — To nineteen — the Intercostales externi et interni, Scalenus 
anticus, Scalenus uicdius, Sc^ilenus posticus, Pectoralis minor, Serratus magnus, Obliquus 
externus ulidominis, (^uadratus lumborum. Diaphragm, Latissimus dorsi, Serratus posticus 
superior, Serratus posticus inferior, Iliocostalis, Musculus accessorius ad iliocostalem, Lon- 
gissimus dorsi, Cervicalis ascendens, Levatores costarum, and Infracostales. 

The Costal Cartilages. 

The costal cartilage (cartilago costalis) (Fig. 122) is white, hyaline cartilage. The 
cartilages serve to prolong the ribs forward to the front of the thorax, and they 
contribute very materially to the elasticity of its walls. The first seven are con- 
nected with the sternum, the next three with the lower border of the cartilage of 
the preceding rib. The cartilages of the last two ribs have pointed extremities, 
W'hich terminate in free ends in the walls of the abdomen. Like the ribs, the 
costal cartilages vary in their length, breadth, and direction. They increase in 
length from the first to the seventh, then gradually diminish to the last. They 
diminish in breadth, as well as the intervals between them, from the first to the 
last. They are broad at their attachment to the ribs, and taper toward their sternal 
extremities, excepting the first two, which are of the same breadth throughout, 
and the sixth, seventh, and eighth, which are enlarged where their margins are 
in contact. In direction they also vary; the first descends a little, the second is 
horizontal, the third ascends slightly, while all the rest follow the course of the 
ribs for a short extent, and then ascend to the sternum or preceding cartilage. 
Each costal cartilage presents two surfaces, two borders, and two extremities. 

Surfaces. — The anterior surface is convex, and looks forward and upward; that 
of the first gives attachment to the costoclavicular ligament and the Subclavius 
muscle; that of the second, third, fourth, fifth, and sixth, at their sternal ends, 
to the Pectoralis major.' The others are covered by, and give partial attachment 
to, some of the great flat muscles of the abdomen. The posterior surface is con- 

1 The first and seventh also, occasionally, give origin to the same muscle. 



166 SPECIAL ANATOMY OF THE SKELETON 

cave, and directed backward and downward, the first giving attachment to the 
Sternothyroid, the third to the sixth inclusive to the Triangularis sterni, and 
the six or seven inferior ones to the Transversalis muscle and the Diaphragm. 

Borders. — Of the two borders, the superior border is concave, the inferior con- 
vex; they afford attachment to the Internal intercostal muscles, the upper border 
of the sixth giving attachment to the Pectoralis major muscle. The contiguous 
borders of the sixth, seventh, and eighth, and sometimes the ninth and tenth, 
costal cartilages present small, smooth, oblong-shaped facets at the points where 
they, articulate. 

Extremities. — Of the two extremities, the outer extremity is continuous with 
the osseous tissue of the rib to which it belongs. The inner extremity of the first 
is continuous with the sternum; the six succeeding ones have rounded extremities, 
which are received into shallow concavities on the lateral margins of the sternum. 
The inner extremities of the eighth, ninth, and tenth costal cartilages are pointed, 
and are connected with the cartilage above. Those of the eleventh and twelfth 
are free and pointed. 

The costal cartilages are most elastic in youth, those of the false ribs being more so than the 
true. In old age they become of a deep yellow color, and are prone to calcify. 

Attachment of Muscles. — To nine — the Subclavius, Sternothyroid, Pectoralis major, 
Internal oblique, Transversalis, Rectus abdominis. Diaphragm, Triangularis sterni, and 
Internal intercostals. 

Surface Form. — The bones of the thorax are to a very considerable extent covered by mus- 
cles, so that in the strongly developed muscular subject they are for the most part concealed. 
In the emaciated subject, on the other hand, the ribs, especially in the lower and lateral region, 
stand out as prominent ridges with the sunken, intercostal spaces between them. 

In the median line, in front, the superficial surface of the sternum is to be felt throughout its 
entire length, at the bottom of a deep median furrow- (the sternal furrow) situated between 
the two great pectoral muscles. These muscles overlap the anterior surface somewhat, so 
that the whole of the sternum in its entire width is not subcutaneous; and this overlapping is 
greater opposite the centre of the bone than above and below, so that the furrow is wider at its 
upper and lower parts, but narrower in the middle. The centre of the upper border of the ster- 
num is visible, constituting the prestemal notch, but the lateral parts of this border are 
obscured by the tendinous origins of the Sternomastoid muscles, which present themselves 
as oblique tendinous cords, which narrow and deepen the notch. Lower down on the sub- 
cutaneous surface, a well-defined transverse ridge, the angulus Ludovici, is always to be felt. 
This denotes the line of junction of the manubrium and the body of the bone, and is a useful 
guide to the second costal cartilage, and thus to the identity of any given rib. The second rib 
being found through its costal cartilage, it is easy to count downward and find any other. From 
the middle of the sternum the furrow spreads out, and, exposing more of the surface of the 
body of the bone, terminates below in a sudden depression, the infrastemal depression, or 
pit of the stomach {scrohiculus cordis), which corresponds to the ensiform cartilage. This 
depression lies between the cartilages of the seventh ribs, and in it the ensiform cartilage may 
be felt. The sternum in its vertical diameter presents a general convexity forward, the most 
prominent point of which is at the joint between the manubrium and gladiolus. 

On each side of the sternum the costal cartilages and ribs on the front of the thorax are par- 
tially obscured by the great jiectoral muscles, through which, however, they are to be felt as 
ridges, with yielding intervals between them, corresponding to the intercostal spaces. Of these 
spaces, the one between the second and third ribs is the widest, the next two somewhat nar- 
rower, and the remainder, with the exception of the last two, comparatively narrow. 

The lower border of the Pectoralis major muscle corresponds to the sixth rib, and below 
this, on the front of the thorax, the broad, flat outline of the ribs as they begin to ascend, and 
the more rounded outline of the costal cartilages, are often visible. The lower boundary of 
the front of the thorax, the abdominothoracic arch, which is most plainly seen by arching 
the body backward, is formed by the ensiform cartilage and the cartilages of the seventh, eighth, 
ninth, and tenth ribs, and the extremities of the eleventh and twelfth ribs or their cartilages. 

On each side of the thorax, from the axilla downward, the flattened external surfaces of the 
ribs may be defined in the form of oblique ridges, separated by depressions corresponding to the 
intercostal spaces. They are, however, covered by muscles, which obscure their outline to a 
certain extent in the strongly developed. Nevertheless, the ribs, with the exception of the first, 
can generally be followed over the front and sides of the thorax without difficulty. The first rib, 
being almost completely covered by the clavicle and scapula, can only be distinguished in a 



THE COSTAL CARTILAGES 107 

small portion of its extent. At the back the angles of the ribs form a slightly marked oblique 
line on each side of and some distance from the vertebral spines. This line diverges some- 
what as it descends, and external to it is a broad, convex surface caused by the projection of 
the ribs beyond their angles. Over this surface, except where covered by the scapula, the 
individual ribs can be distinguished. 

Applied Anatomy. — Malformations of the sternum present nothing of surgical importance 
beyond the fact that abscesses of the mediastinum may sometimes escape through the sternal 
foramen. Fractures of the sternum are by no means common, due, no doubt, to the elasticity 
of the ribs and their cartilages, which support it like so many springs. When broken it is fre- 
quently associated with fracture of the vertebral column, and may be caused by forcibly bending 
the body either backward or forward until the chin becomes impacted against the top of the 
sternum. It may also be fractured by direct violence or by muscular action. The fracture 
usually occurs in the upper half of the body of the bone. Dislocation of the gladiolus from the 
manubrium also takes place, and is sometimes described as a fracture. 

The bone, cancellous in structure and being subcutaneous, is frequently the seat of (jiimma- 
tous tumors, and not uncommonly is affected with caries. Occasionally the bone, and especially 
its ensiform appendix, becomes altered in shape and driven inward, in workmen, by the 
pressure of tools against the chest. 

The rihs are frequently broken, though from their connections and shape they are able to 
withstand great force, yielding under the injury and recovering themselves like a spring. The 
middle of the series are the ones most liable to fracture. The first, and to a less extent the 
second, being protected by the clavicle, are rarely fractured; and the eleventh and twelfth, on 
account of their loose and floating condition, enjoy a like immunity. The fracture generally 
occurs from indirect violence, from forcible compression of the thoracic wall, and the bone then 
gives way at its weakest part — i. e., just in front of the angle. But the ribs may also be broken 
by direct violence, when the bone gives way and is driven inward at the point struck, or they 
may be broken by muscular action. It seems probable, however, that in the latter case the 
bone has undergone some atrophic changes. Fracture of the ribs is frequently complicated by 
some injury to the viscera contained within the thorax or upper part of the abdominal cavity, 
and this is most likely to occur in fractures from direct violence. Occasionally supernumerary 
ribs exist. They may come from the lumbar vertebrse or from the cervical vertebrse. A cervical 
rib is due to excessive development of the costal element of the seventh cervical vertebra. 
In nearly two-thirds of the reported cases the condition is bilateral. It rarely produces symp- 
toms until after the twentieth year. The symptoms are a superficial pulsation of the sub- 
clavian artery, a prominence which can be felt, and evidences of pressure in the brachial plexus 
(Carl Beck). Beck divides the different types of the condition as follows: (a) Slight degree: 
The cervical rib reaches beyond the transverse process. (6) More advanced : The cervical rib 
reaches beyond the transverse process, either with a free end or touching the first rib. (c) 
Almost complete: The connection between the cartilage of the first rib is formed either by 
means of a distinct band or by the end of its long body, {d) Complete: It has become a true 
rib and possesses a true cartilage which unites with the cartilage of the first rib.' A very rare 
condition is a rib from the sixth cervical vertebra. The diagnosis is confirmed by the .r-rays. 
The treatment of cervical rib is excision. 

Fracture of the costal cartilages may also take place, though it is a comparatively rare injury. 

The thorax is frequently found "to be altered in shape in certain diseases. The shape 
of the thorax in those suffering from rhachitis is produced chiefly by atmospheric pressure. 
The balance between the air on the inside of the thorax and the air on the outside during 
some stage of respiration is not equal, the preponderance being in favor of the air outside; 
and this, acting on the softened ribs, causes them to be forced in at the junction of the carti- 
lages with the bones, which is the weakest part. In consequence of this the sternum projects 
forward with a deep depression on either side caused by the sinking in of the softened ribs. 
The depression is less on the left side, on account of the rijas being supported by the heart. The 
condition is known as pigeon-h-east. The lower ribs, however, are not involved in this deform- 
ity, as they are prevented from falling in by the presence of the stomach, liver, and spleen. And 
when the liver and spleen are enlarged, as they sometimes are in rhachitis, the lower ribs may be 
pushed outward; this causes a transverse constriction just above the costal arch. The anterior 
extremities of the ribs are usually enlarged in rhachitis, giving rise to what has been termed the 
rhachitio rosary. The phthisical chest is often long and narrow, flattened from before backward, 
and with great obliquity of the ribs and projection of the scapute. In pulmonary emphysrma 
the thorax is enlarged in all its diameters, and presents on section an almost circular outline. It 
has received the name of the barrel-shaped chest. In severe cases of lateral curvature of the 
spine the thorax becomes much distorted. In consequence of the rotation of the bodies of the 
vertebrre which takes place in this disease the ribs opposite the convexity of the thoracic curve 
become extremely convex behind, being thrown out and bulging, and at the same time flattened 

' Jour. .\mer. Med. Assoc, June 17, 1905. 



168 SPECIAL ANATOMY OF THE SKELETON 

in front, so that the two bends of the same rib are almost parallel. Coincident with this, the 
ribs on the opposite side, on the concavity of the curve, are sunken and depressed behind and 
bulging and convex in front. In addition to this the ribs become occasionally welded together 
by bony material. 

The ribs are frequently the seat of caries leading to abscesses and sinuses, which may burrow- 
to a considerable extent over the wall of the thorax. The only special anatomical point in con- 
nection with abscesses and sinuses is that care must be taken in dealing with them that the 
intercostal space is not punctured and the pleural cavity opened or the intercostal vessels 
wounded, as the necrosed portion of bone is generally situated on the internal surface of the rib. 

In cases of empyema the thorax requires opening to evacuate the pus. There is considerable 
difference of opinion as to the best position to do this. Probably the best place for intercostal 
drainage is between the fifth and sixth ribs, in or a little in front of the mid-axillary line. This 
is the last part of the cavity to be closed by the expansion of the lung; it is not thickly covered 
by soft parts; the space between the two ribs is sufficiently great to allow of the introduction of 
a fair-sized drainage tube, and when the patient is confined to bed he does not lie upon the 
drainage tube as he does when the opening is posterior. Better than intercostal drainage in the 
vast majority of cases is rib resection and drainage. A portion of the fifth or sixth rib should 
be removed in the mid-axillaiy line. In chronic empyema the lung becomes shrunken and ad- 
herent, and simple drainage will not bring about a cure. It is necessary in such cases to do an 
operation that will permit of collapse of the chest wall. Estlander s operation consists in resect- 
ing a portion of every rib which overlies the cavity of the empyema. Schede's operation consists 
in removing ribs from the second rib down over the empyema cavity. The ribs are removed 
from cartilages to angles, and intercostal muscles and the parietal layer of the pleura are also 
taken away. Fowler and de Lorme not only practise extensive rib resection and remove the 
parietal layer of the pleura, but also remove pulmonary pleura (total pleurectomy or pulmonary 
decortication). 

THE EXTREMITIES. 

The extremities, or limbs, are those long, jointed appendages of the body 
which are connected to the trunk by one end and free in the rest of their extent. 
They are four in number: an upper or thoracic pair, connected with the thorax 
through the intervention of the shoulder and subservient mainly to prehension; 
and a lower or pelvic pair, connected with the pelvis, intended for support and 
locomotion. Both pairs of limbs are constructed after one common type, so that 
they present numerous analogies, while at the same time certain differences are 
observed between the upper and lower pair, dependent on the peculiar offices 
they have to perform. 

The bones by which the upper and lower limbs are attached to the trunk are 
named, respectively, the shoulder and pelvic girdles, and they are constructed on the 
same general type, though presenting certain modifications relating to the diflerent 
uses to which the upper and lower limbs are respectively applied. The shoulder 
girdle is formed by the scapula and clavicles, and is imperfect in front and behind. 
In front, however, the girdle is completed by the upper end of the sternum, with 
which the inner extremities of the clavicle articulate. Behind, the girdle is widely 
imperfect and the scapula is connected to the trunk by muscles only. The pelvic 
girdle is formed by the innominate bones, and is completed in front through the 
symphysis pubis, at which the two innominate bones articulate with each other. 
It is imperfect behind, but the intervening gap is filled in by the upper part of 
tlie sacrum. The pelvic girdle, therefore, presents, with the sacrum, a complete 
ring, massive and comparatively rigid, in marked contrast to the lightness and 
mobility of the shoulder girdle. 

THE UPPER EXTREMITY. 

The bones of the upper extremity consist of the clavicle and scapula (pectoral 
girdle), the humerus (arm), the radius and ulna (forearm), the carpal bones 
(wrist), the metacarpal bones (palm), and the phalanges (digits). 



THE CLA VICLE, OB COLLAR BONE ](J9 

THE SHOULDER GIRDLE. 

The shoulder girdle consists of the clavicle and the scapula. 

The Clavicle, or Collar Bone (Clavicula). 

The clavicle forms the anterior portion of the shoulder girdle. It is a long 
bone, curved somewhat like the italic letter /, and placed nearly horizontally at 
the upper and anterior part of the thorax, immediately over the first rib. It 
articulates by its inner extremity with the upper border of the sternum, and by 
its outer extremity with the acromion process of the scapula, serving to sustain 
the upper extremity in the various positions which it assumes, while at the same 
time it allows of great latitude of motion in the arm.' It presents a double curva- 
ture when looked at in front, the convexity being forward at the sternal end and 
the concavity at the scapular end. Its outer third is flattened from above downward, 
and extends, in the natural position of the bone, from a point opposite the cora- 
coid process to the acromion. Its inner two-thirds are of a prismatic form, 
and extend from the sternum to a point opposite the coracoid process of the scapula. 

Outer or Flattened Portion. — The outer third is flattened from above down- 
ward, so as to present two surfaces, an upper and a lower; and two borders, an 
anterior and a posterior. 

Surfaces. — The upper surface is flat, rough, marked by impressions for the 
attachment of the Deltoid in front and the Trapezius behind; between these two 
impressions a small portion of the bone is subcutaneous. The under surface is 
flattened. At its posterior border, a little external to the point where the pris- 
matic joins with the flattened portion, is a rough eminence, the conoid tubercle 
(tuberositas coracoidea) ; this, in the natural position of the bone, surmoimts the 
coracoid process of the scapula and gives attachment to the conoid ligament. 
From' this tubercle an oblique line, occasionally a depression, passes forward 
and outward to near the outer end of the anterior border; it is called the oblique 
line or trapezoid ridge, and aflfords attachment to the trapezoid ligament. 

Borders. — The anterior border is concave, thin, and rough, and gives attachment 
to the Deltoid; it occasionally presents, at its inner end, at the commencement of 
the deltoid impression, a tubercle, the deltoid tubercle. The posterior border is 
convex, rough, broader than the anterior, and gives attachment to the Trapezius. 

Inner or Prismatic Portion. — The prismatic portion forms the inner two- 
thirds of the bone. It is curved so as to be convex in front, concave behind, and 
is marked by three borders, separating three surfaces. 

Borders. — The anterior border is continuous with the anterior margin of the flat 
portion, and separates the anterior surface from the inferior; at the inner half 
of the clavicle it forms the lower boundary of an elliptical space for the attach- 
ment of the clavicular portion of the Pectoralis major, and approaches the pos- 
terior border of the bone; it coincides with the anterior margin of the subclavian 
groove. The superior border is continuous with the posterior margin of the flat 
portion, and separates the anterior from the posterior surface. At its commence- 
ment it is smooth and rounded, becomes rough toward the inner third for tlie 
attachment of the Sternomastoid muscle, and terminates at the upper angle of 
the sternal extremity. The posterior or subclavian border separates the posterior 

> The clavicle acts especially as a fulcrum to enable the muscles to give lateral motion to the arm. It is 
accordingly absent in those animals in which the fore limbs are used only for progression, but is present for the 
most part in those animals in which the anterior extremities are clawed and used for prehension, though m some 
of them— as, for instance, in a large number of the carnivora— it is merely a rudimentary bone suspended among 
the muscles, and not articulating with the scapula or sternum. 



170 



SPECIAL ANA TOMY OF THE SKELETON 



from the inferior surface, and extends from the conoid tubercle to the rhomboid 
impression. It forms the posterior boundary of the groove for the Subclavius 
muscle, and gives attachment to a layer of cervical fascia covering the Omohyoid 
muscle. 

Surfaces. — The anterior surface is included betw^een the superior and anterior 
borders. It is directed forward and a little upward at the sternal end, outward 
and still more upward at the acromial extremity, where it becomes continuous 
with the upper surface of the flat portion. Externally, it is smooth, convex, 
nearly subcutaneous, being covered only by the Platysma; but, corresponding 
to the inner half of the bone, it is divided by a more or less prominent line into 
two parts — a lower portion, elliptical in form, rough, and slightly convex, for the 
attachment of the Pectoralis major; and an upper part, which is rough, for 
the attachment of the Sternomastoid. Between the two muscular impressions 



Aaonual exfremiti/. 



Sternal extremity. 




Fig. 136. — Left clavicle. Superior surface. 



Capsidar 
ligament 




Fig. 137. — Left clavicle. Inferior surface. 



is a small subcutaneous interval. The posterior or cervical surface is smooth, 
flat, and looks backward toward the root of the neck. It is limited, above, by the 
superior border; below, by the posterior border; internally, by the margin of the 
sternal extremity; externally, it is continuous with the posterior border of the flat 
portion. It is concave from within outward, and is in relation, by its lower part, 
with the suprascapular vessels. This surface, at about the junction of the inner 
and outer curves, is also in close relation with the brachial plexus and subclavian 
vessels. It gives attachment, near the sternal extremity, to part of the Sternohyoid 
muscle; and presents, at or near the middle, a nutrient foramen. It opens into 
a nutrient canal, which is directed obliquely outward and transmits the chief 
nutrient artery of the bone. Sometimes there are two foramina on the poste- 
rior surface, or one on the posterior and one on the inferior surface. The infe- 
rior or subclavian surface is bounded, in front, by the anterior border; behind, 



THE CLAVICLE, OR COLLAR BONE 171 

by the posterior border. It is narrow internally, but gradually increases in 
width externally, and is continuous with the under surface of the flat portion. 
Commencing at the sternal extremity may be seen a small facet, the costal facet, 
for articulation with the cartilage of the first rib. This is continuous with the 
articular surface at the sternal end of the bone. External to this is a broad, rough 
surface, the rhomboid impression (tuberositas costalis), rather more than an inch 
in length, for the attachment of the costoclavicular (rhomboidj ligament. The 
remaining part of this surface is occupied by a longitudinal groove, the subclavian 
groove, broad and smooth externally, narrow and more uneven internally; it gives 
attachment to the Subclavius muscle, and by its margins to the costocoracoid 
membrane, which splits to enclose the muscle. Not infrequently this groove is 
subdivided into two parts by a longitudinal line, which gives attachment to the 
intermuscular septum of the Subclavius muscle. 

Internal or Sternal Extremity (extremitas sternalis). — The internal or sternal 
extremity of the clavicle is triangular in form, directed inward and a little down- 
ward and forward; and presents an articular facet (fades articularis sternalis), 
concave from before backward, convex from above downward, which articulates 
with the sternum through the intervention of an intra-articular fibrocartilage; 
the circumference of the articular surface is rough, for the attachment of numer- 
ous ligaments. The posterior border of this surface is prolonged backward, so 
as to increase the size of the articular facet; the upper border gives attachment 
to the intra-articular fibrocartilage, and the lower border is continuous with the 
costal facet on the inner end of the inferior surface, which articulates with the 
cartilage of the first rib. 

Outer or Acromial Extremity (extremitas acromialis). — The outer or acromial 
extremity, directed outward and forward, presents a small, flattened, oval facet, 
acromial surface (fades articularis acromialis), which looks obliquely downward, 
and which articulates with the acromion process of the scapula. The circum- 
ference of the articular facet is rough, especially above, for the attachment of 
the acromioclavicular ligaments. 

Peculiarities of the Bone in the Sexes and in Individuals.— In the female the clavicle 
is generally shorter, thinner, less curved, and .siiioolhei- than in the male; in the female it is 
placed almost, if not quite, horizontal, while in the male it inclines slightly downward and inward. 
In those persons who perform considerable manual labor, which brings into constant action the 
muscles connected with this bone, it becomes thicker and more curved, its ridges for muscle 
attachment become prominently marked. The right clavicle is generally longer, thicker, and 
rougher than the left. 

Structure. — The shaft, as well as the extremities, consists of cancellous tissue, invested by a 
coni|ia(t layer much thicker in the middle than at either end. It has no true medullary cavity. 

Development. — From two centres, one for the shaft and outer extremity and one for the 
st<Tnal cxtreraity. The primary centre for the shaft appears very early, before that of any 
other bone, at about the fifth or sixth week of fetal life. The secondary centre for the sternal 
end makes its appearance about the fifteenth to the twentieth year, and unites with the rest of 
the bone about the twenty-fifth year. 

Articulations. — With the sternum, scapula, by intra-articular fibrocartilaginous disks, and 
with tiie cartilage of the first rib. 

Attachment of Muscles. — To six — the Sternomastoid, Trapezius, Pectoralis major, 
Deltoid, Subclavius, and Sternohyoid. 

Surface Form. — The clavicle can be felt throughout its entire length, even in persons who 
are very fat. Commencing at the inner end, the enlarged sternal extremity, where the bone 
projects above the upper margin of the sternum, can be felt, forming with the sternum and the 
rounded tendon of the Sternomastoid a V-shaped notch, the presternal notch. Passing out- 
ward, the shaft of the bone can be felt immediately under the skin, with its convexity forward 
in the inner two-thirds, the surface partially obscured above and below^ by the attachments of 
the Sternomastoid and Pectoralis major muscles. In the outer third it forms a gentle curve 
backward, and terminates at the outer end in a somewhat enlarged extremity which articulates 
with the acromial process of the scapula. The direction of the clavicle is almost, if not quite, 
horizontal when the arm is lying quietly by the side, though in well-developed subjects it may 



172 SPECIAL ANATOMY OF THE SKELETON 

incline a little upward at its outer end. Its direction is, however, very changeable, altering with 
the varying movements of the shoulder-joint. 

Applied Anatomy. — The clavicle is the most he(\\iexit\y fractured of any single bone in the 
body. This is due to the fact that it is much exposed to violence, and is the only bony connec- 
tion between the upper limb and the trunk. The bone, moreover, is slender, and is very super- 
ficial. The bone may be broken by direct or indirect violence or by muscular action. The most 
common cause is, however, from indirect violence, and the bone then gives way at the junction 
of the fi.xed outer one-third with the movable inner two-thirds of the bone. This is the weakest 
and most slender part of the bone. The fracture is generally oblique, and the displacement 
of the outer fragments is inward, away from the surface of the body; hence, compound fracture 
of the clavicle is of rare occurrence. The inner fragment, as a rule, is little displaced. Beneath 
the bone the main vessels of the upper limb and the great nerve cords of the brachial plexus 
lie on the first rib, and are liable to be wounded in fracture, especially in fracture from direct 
violence, when the force of the blow drives the broken ends inward. Fortunately, the Subclavius 
muscle is interposed between these structures and the clavicle, and this often protects them 
from injury. 

The clavicle is not uncommonly the seat of sarcomatous tumors, rendering the operation 
of excision of the entire bone necessary. This operation is best performed by exposing the 
bone freely, disarticulating at the acromial end, and turning it inward. The removal of 
the outer part is comparatively easy, but resection of the inner part is fraught with difficulty, 
the main danger being the risk of wounding the great veins which are in relation with its • 
under surface. 

The Scapula, or Shoulder Blade. 

The scapula forms the back part of the shoulder girdle. It is a large flat bone, 
triangular in shape, situated at the posterior aspect and side of the thorax, between 
the second and seventh or sometimes the eighth rib, its internal border or base 
being about an inch from and nearly but not quite parallel with the spinous pro- 
cesses of the vertebrse, so that it is rather closer to them above than below. It 
presents for examination two surfaces, three borders, and three angles. 

Surfaces. — The anterior or ventral surface (fades costalis) (Fig. 138) presents 
a broad concavity, the subscapular fossa (fossa subscapular is). It is marked, in 
the inner two-thirds, by several oblique ridges (lineae musculares), which pass 
outward and upward; the outer third is smooth. The oblique ridges give origin 
to the tendinous intersections, and the surfaces between them to the fleshy fibres, 
of the Subscapularis muscle. The outer third of the fossa is smooth, is covered 
by, but does not afford attachment to, the fibres of this muscle. This surface is 
separated from the internal border by a smooth, triangular margin at the supe- 
rior and inferior angles, and in the interval between these by a narrow edge which 
is often deficient. This marginal surface aft'ords attachment throughout its entire 
extent to the Serratus magnus muscle. The subscapular fossa presents a trans- 
verse depression at its upper part, where the bone appears to be bent on itself, 
forming a considerable angle, called the subscapular angle, thus giving greater 
strength to the body of the bone from its arched form, while the summit of the 
arch serves to support the spine and acromion process. It is in this situation 
that the fossa is deepest, so that the thickest part of the Subscapularis muscle 
lies in a line perpendicular to the plane of the glenoid cavity, and must conse- 
quently operate most effectively on the head of the humerus, which is contained 
in that cavity. 

The posterior or dorsal surface (fades dorsal is) (Fig. 139) is arched from above 
downward, alternately concave and convex from side to side. It is subdivided 
unequally into two parts by the spine; the portion above the spine is called the 
supraspinous fossa, and that below it the infraspinous fossa. 

The supraspinous fossa (fossa supraspinata), the smaller of the two, is concave, 
smooth, and broader at the vertebral than at the humeral extremity. It affords 
attachment by its inner two-thirds to the Supraspinatus muscle. 

The infraspinous fossa (fossa infraspinata) is much larger than the preceding; 



THE SCAPULA,' OR SHOULDER BLADE 



173 



toward its vertebral margin a shallow concavity is seen at its upper part; its centre 
presents a prominent convexity, while toward the axillary border is a deep groove 
which runs from the upper toward the lower part. The inner two-thirds of this 
surface affords origin to the Infraspinatus muscle; the outer third is only covered 
by it, without giving attachment to its fibres. This surface is separated" from the 
axillary border by an elevated ridge, which runs from the lower margin of the glenoid 



Coraco-aCTora ial 
ligament 




Fig. 138. — Left scapula. Anterior surface or venter. 

cavity downward and backward to the internal border, about an inch above the 
inferior angle. The ridge serves for the attachment of a strong aponeurosis which 
separates the Infraspinatus from the two Teres muscles. The surface of bone 
between this line and the axillary border is narrow in the upper two-thirds of its 
extent, and traversed near its centre by a groove for the passage of the dorsalis 
scapulae vessels; it affords origin to the Teres minor muscle. Its lower third 



174 



SPECIAL ANATOMY OF THE SKELETON 



presents a broader, somewhat triangular surface, which gives origin to the Teres 
major, and over which the I>atissimus dorsi glides; sometimes the latter muscle 
takes origin by a few fibres from this part. The broad and narrow portions of 
bone above alluded to are separated by an oblique line which runs from the axillary 
border, downward and backward, to meet the elevated ridge; to it is attached the 
aponeurosis separating the two Teres muscles from each other. 



Coracohumeral 
ligament 



Coracoacromial ligament 
Trapezoid ligament 
Conoid ligament 




Fig. 139.— Left scapula 



Posterior surface or dorsum. 



The spine (spina scapulae) is a prominent plate of bone which crosses obliquely 
the inner four-fifths of the dorsum of the scapula at its upper part, and separates 
the supra- from the infraspinous fossa; it commences at the vertebral border by a 
smooth, triangular surface, over which the Trapezius glides, and; gradually be- 
coming more elevated as it passes outward, terminates in the acromion process 
which overhangs the shoulder-joint- The spine is triangular and flattened from 



THE SCAPULA, OB SHOULDER BLADE 175 

above downward, its apex corresponding to the vertebral border, its base (which 
is directed outward) to the neck of the scapula. It presents two surfaces and three 
borders. Its superior surface is concave, assists in forming tiie supraspinous 
fossa, and affords attachment to part of the Supraspinatus muscle. Its inferior 
surface forms part of the infraspinous fossa, gives origin to part of the Infraspi- 
natus muscle, and presents near its centre the orifice of a nutrient canal. Of the 
three borders, the anterior is attached to the dorsum of the bone; the posterior, 
or crest of the spine, is broad, and presents two lips and an intervening rough 
interval. To the superior lip is attached the Trapezius to the extent shown in 
Fig. 139. A rough tubercle is generally seen occupying that portion of the spine 
which receives the insertion of the middle and inferior fibres of this muscle. From 
the inferior Up, throughout its whole length, arises the Deltoid. The interval 
between the lips is also partly covered by the tendinous fibres of these muscles. 
The external border, or base, the shortest of the three, is slightly concave, its edge 
thick and round, continuous above with the under surface of the acromion process, 
below with the neck of the scapula. The narrow portion of bone external to this 
border, and separating it from the glenoid cavity, is called the great scapular notch, 
and serves to connect the supra- and infraspinous fosste. 

The acromion process (acromion) is a large and somewhat triangular or oblong 
process, flattened from behind forward, directed at first a little outward, and then 
curving forward and upward, so as to overhang the glenoid cavity. Its upper 
surface, directed upward, backward, and outward, is convex, rough, and gives 
origin to some fibres of the Deltoid, and in the rest of its extent it is subcutaneous. 
Its under surface is smooth and concave. Its outer border is thick and irregular, 
and presents three or four tubercles for the tendinous origins of the Deltoid 
muscle. Its inner margin, shorter than the outer, is concave, gives attachment 
to a portion of the Trapezius muscle, and presents about its centre a small oval 
surface for articulation with the acromial end of the clavicle. Its apex, which 
corresponds to the point of meeting of these two borders in front, is thin, and has 
attached to it the coracoacromial ligament. 

Margins, or Borders of the Scapula. — The superior border (margo superior) is 
the shortest and thinnest of the three borders; it is concave and extends from the 
internal ang'e to the coracoid process. At its outer part is a deep, semicircular 
notch, the suprascapular notch (i.ncisura scapxdae), formed partly by the base 
of the coracoid process. The notch is converted into a foramen by the supra- 
scapular ligament, and serves for the passage of the suprascapular nerve. Some- 
times this foramen is entirely surrounded by bone. The adjacent margin of the 
superior border affords attachment to the Omohyoid muscle. 

The external or axillary border (margo axillaris) is the thickest of the three. It 
commences above at the lower margin of the glenoid cavity, and inclines obliquely 
downward and backward to the inferior angle. Immediately below the glenoid 
cavity is a rough impression, the infraglenoid tubercle {tuberositas itifraglenoidalis), 
about an inch in length, which affords origin to the long head of the Triceps muscle; 
in front of this is a longitudinal groove, which extends as far as the lower third 
of the external border and afl^ords origin to part of the Subscapularis muscle. 
The inferior third of this border, which is thin and sharp, serves for the origin 
of a few fibres of the Teres major behind and the Subscapularis in front. 

The internal or vertebral border (margo vertebralis) is the longest of the three, 
and extends from the internal to the inferior angle of the bone. It is arched, is 
intermediate in thickness between the superior and the external borders, and the 
portion of it above the spine is bent considerably outward, so as to form an obtuse 
angle with the lower part. The internal border presents an anterior lip, a posterior 
lip, and an intermediate space. The anterior lip affords attachment to the Serratus 
magnus; the posterior lip, an origin to the Supraspinatus above the spine, the 



176 SPECIAL ANATOMY OF THE SKELETON 

Infraspinatus below; to the interval between the two lips, the Levator anguli 
scapulae is inserted; above the triangular surface at the commencement of the spine, 
the Rhomboideus minor to the edge of that surface; the Rhomboideus major 
is attached by means of a fibrous arch connected above to the lower part of 
the triangular surface at the base of the spine, and below to the lower part of the 
posterior border. 

Angles.— The internal angle (angulus medialis), formed by the junction of the 
superior and internal borders, is thin, smooth, rounded, somewhat inclined 
outward, and gives attachment to a few fibres of the Levator anguli scapulae 
muscle. 

The inferior angle (angulus inferior), thick and rough, is formed by the union 
of the vertebral and axillary borders, its posterior surface affording origin to the 
Teres major and frequently to a few fibres of the Latissimus dorsi. 

The external angle {angulus lateralis) is the thickest part of the bone, and forms 
what is called the head of the scapula. The head presents a shallow, pyriform, 
articular surface, the glenoid surface (cavitas glenoi'dalis) , the longest diameter 
of which is from above downward, and its direction outward and forward. It 
is broader below than above. Just above it is a rough surface, the supra- 
glenoid tubercle {tuberositas supraglenoidalis) , from which arises the long 
tendon of the Biceps muscle. The glenoid cavity is covered with cartilage in 
the recent state; and its margins are slightly raised and give attachment to a 
fibrocartilaginous structure, the glenoid ligament, by which its cavity is deepened. 
The neck of the scapula {collum scapulae) is the slightly depressed surface which 
surrounds the head; it is more distinct on the posterior than on the anterior surface, 
and below than above. In the latter situation it has arising from it a thick promi- 
nence, the coracoid process. 

The coracoid process {processus coracoideus) is a thick, curved process of bone 
which arises by a broad base from the upper part of the neck of the scapula; it 
is directed at first upward and inward, then, becoming smaller, it changes its 
direction and passes forward and outward. The ascending portion, flattened from 
before backward, presents in front a smooth, concave surface over which passes 
the Subscapularis muscle. The horizontal portion is flattened from above 
downward, its upper surface is convex and irregular; its under surface is smooth; 
its inner border is rough, and gives attachment to the Pectoralis minor; its outer 
border is also rough for the coracoacromial ligament, while the apex is embraced 
by the conjoined tendon of origin of the short head of the Biceps and of the 
Coracobrachialis and gives attachment to the costocoracoid ligament. At the 
inner side of the root of the coracoid process is a rough impression for the attach- 
ment of the conoid ligament; and running from it obliquely forward and outward 
on the upper surface of the horizontal portion, an elevated ridge for the attachment 
of the trapezoid ligament. 

Structure. — In the head, processes, and all the thickened parts of the bone the scapula is 
composed of cancellous tissue covered by compact bone, while in the rest of its extent it is com- 
posed of a thin layer of dense, compact tissue. The central part of the supraspinous fossa and 
the upper part of the infraspinous fossa, but especially the former, are usually so thin as to 
be semitransparent; occasionally the bone is found wanting in this situation, and the adjacent 
muscles come into contact. 

Development (Fig. 140). — From seven, or more centres — one for the body, two for the 
coracoid process, two for the acromion, one for the vertebral border, and one for the inferior 
angle. Ossification of the body of the scapula commences about the second month of fetal life 
by the formation of an irregular quadrilateral plate of bone immediately behind the glenoid 
cavity. This plate extends itself so as to form the chief part of the bone, the spine growing 
up from its posterior surface about the third month. At birth a large part of the scapula is 
osseous, but the glenoid cavity, coracoid and acromion processes, the posterior border, and 
inferior angle are cartilaginous. From the fifteenth to the eighteenth month after birth 



THE SCAPULA, OB SHOULDER BLADE 



177 



ossification takes place in the middle of the coracoid process, which usually becomes joined wilii 
the rest of the bone at the time when the other centres make their appearance. Between the 
fourteenth and twentieth years ossification of the remaining centres takes place in quick 
succession, and in the following oviei-: fir.-it, in the root of the coracoid process, in the form of 
a broad scale; second, near the base of the acromion process; third, in the inferior ande and 
contiguous part of the posterior hor Aev; fourth, near the extremity of the acromion; fifth, 
in the posterior border. The acromion process, besides being formed of two separate nuclei, 
has its base formed by an extension into it of the centre of ossification which belongs to the 
spine, the extent of which varies in different cases. The two separate nuclei unite and then 
join with the extension from the spine. These various epiphyses become joined to the bone 
between the ages of twenty-two and 
twenty-five years. Sometimes fail- 
ure of union between the acromion 
process and spine occurs, the junc- 
tion being effected by fibrous tissue 
or by an imperfect articulation; in 
some cases of supposed fracture 
of the acromion with ligamentous 
union it is probable that the de- 
tached segment was never united to 
the rest of the bone. The upper 
third of the glenoid cavity is usually 
ossified from a separate centre {suh- 
coracoid) which makes its appearance 
between the tenth and eleventh 
years. Very often, in addition, an 
epiphysis appears for the lower part 
of the glenoid cavity. 

Articulations. — With the hu- 
merus and clavicle. 

Attachment of Muscles. — To 
seventeen — to the anterior surface, 
theSubscapularis; posterior surface, 
Supraspinatus, Infraspinatus; spine. 
Trapezius, Deltoid; superior border. 
Omohyoid; vertebral border, Serra- 
tus magnus. Levator anguli scapulae, 
Rhomboideus, minor and major; 
axillary border. Triceps, Teres 
minor, Teres major; apex of glen- 
oid cavity, long head of the Biceps; 
coracoid process, short head of the 
Biceps, Coracobrachialis, Pectoralis 
minor; and to the inferior angle oc- 
casionally a few fibres of the Latissi- 
mus dorsi. 

Surface Form.— The only parts 
of the scapula which are truly sub- 
cutaneous are the spine and acro- 
mion process, but, in addition to these, the coracoid process, the internal or vertebral border 
and inferior angle, and, to a less extent, the axillary border, may be defined. The acro- 
mion process and spine of the scapula are easily felt throughout their entire length, forming, 
with the clavicle, the arch of the shoulder. The acromion can be ascertained to be connected 
to the clavicle at the acromioclavicular joint by running the finger along it, its position being 
often indicated by an irregularity or bony outgrowth from the clavicle close to the joint. The 
acromion can be felt forming the point of the shoulder, and from this can be traced backward to 
join the spine of the scapula. The place of junction is usually denoted by a prominence, which 
is sometimes called the acromial angle. From here the spine of the scapula can be felt as a 
prominent ridge of bone, marked on the surface as an oblique depression, which becomes less 
and less distinct, and terminates a little external to the spinous processes of the vertebra?. Its 
termination is usually indicated by a slight dimple in the skin on a level with the interval be- 
tween the third and fourth thoracic spines. Below this point the vertebral border of the scapula 
may be traced, running downward and outward, and thus diverging from the vertebral spines, 
to the inferior angle of the bone, which can be recognized, although covered by the Latissimus 
dorsi muscle. From this angle the axillary border can usually be traced through this thick 
muscular covering, forming, with the muscles, the posterior fold of the axilla. The coracoid 




ifenof 



Fig. 140. — Plan of the development of the scapula. From 
seven centres. The epiphyses (except one for the coracoid pro- 
cess) appear from fifteen to seventeen years, and unite between 
twenty-two and twenty-five years of age. 



178 SPECIAL ANA TOMY OF THE SKELETON 

process may be felt about an inch below the junction of the middle and outer thirds of the 
clavicle. Here it is covered by the anterior border of the Deltoid and lies a little to the outer 
side of a slight depression which corresponds to the interval between the Pectoralis major 
and Deltoid muscles. When the arms are hanging by the side, the upper angle of the scapula 
corresponds to the upper border of the second rib or the interval between the first and second 
thoracic spines, the inferior angle to the upper border of the eighth rib or the interval between 
the seventh and eighth thoracic spines. 

Applied Anatomy. — Fractures of the body of the scapula are rare, owing to the mobility of 
the bone, the thick layer of muscles \>y which it is encased on both surfaces, and the elasticity of 
the ribs on which it rests. Fracture of the neck of the bone is also uncommon. The most fre- 
quent course of a line of fracture of the neck is from the suprascapular notch to the infraglenoid 
tubercle (surgical neck), and it derives its principal interest from its simulation to a subglenoid 
dislocation of the humerus. The diagnosis can be made by noting the alteration in the position 
of the coracoid process. A fracture 'of the neck external to, and not including, the coracoid 
process (anatomical neck) is said to occur, but it is exceedingly doubtful whether such an 
accident ever takes place. The acromion process is more frequently broken than any other 
part of the bone, and there is sometimes, in young subjects, a separation of the epiphysis. It 
is believed that many of the cases of supposed fracture of the acromion, with fibrous union, 
which have been found on postmortem examination are really cases of imperfectly united 
epiphysis. Sir Astley Cooper believed that most fractures of this bone are united by fibrous 
tissue, and the cause of this mode of union is the difficulty that arises in keeping the fractured 
ends in constant apposition. The coracoid process is occasionally broken oft', either by direct 
violence or perhaps, rarely, by muscular action. 

Tumors of various kinds grow from the scapula. Of the innocent form of tumors, probably 
the osteomata are the most common. ' When an osteoma grows from the anterior surface of the 
scapula, as it sometimes does, it is of the compact variety, such as usually grows from mem- 
brane-formed bones, as the bones of the skull. This would appear to afford evidence that this 
portion of the bone is formed from membrane, and not, like the rest of the bone, from cartilage. 
Sarcomatous tumors sometimes grow from the scapula, and may necessitate removal of the bone, 
with or without amputation of the upper limb. Removal of the upper limb with the scapula and 
the outer two-thirds of the clavicle is known as the mterscaqndothoracic amputafion. The scapula 
may be partially resected or completely excised. There are several methods of complete excision. 
The bone may be excised by a T-shaped incision, and, the flaps being reflected, the removal is 
commenced from the vertebral border, so that the subscapular vessels which lie along the axillary 
border are among the last structures divided, and can be at once secured. 



THE ARM. 

The arm is that portion of the upper extremity which is situated between the 
shoulder and the elljow. Its skeleton consists of a single bone, the humerus. 

The Humerus, or Arm Bone (Figs. 141, 142). 

The humerus is the longest and largest bone of the upper extremity; it presents 
for examination a shaft and two extremities. 

Upper or Proximal Extremity. — The upper extremity presents a large, 
rounded head, joined to tlie shaft by a constricted portion, called the neck, and 
two other eminences, the greater and lesser tuberosities. 

The Head (caput humeri). — ^The head, nearly hemispherical in form,^ is dii'ected 
upward, inward, and slightly backward, and articulates with the glenoid surface 
of the scapula; its surface is smooth and coated with cartilage in the recent state. 
The circumference of its articular surface is slightly constricted, and is termed 
the anatomical neck, in contradistinction to the constriction which exists below the 
tuberosities. The latter is called the surgical neck (collum chirurgicuvi) , as it is 
often the seat of fracture. 

The anatomical neck (collum anatomicum) is obliquely directed, forming an 

1 Though the head is nearly hemispherical in form, its margin, as Sir G. Humphry has shown, is by no means 
a true circle. Its greatest measurement is from the top of the bicipital groove in a direction downward, inward, 
and backward. Hence, it follows that the greatest elevation of the arm can be obtained by rolling the articular 
surface in this direction — that is to say, obliquely upward, outward, and forward. 



THE HUMERUS, OB ABM BONE 



179 



Capsular ligament 




[brevis]. 



Fig. 141. — Left humerus. Anterior view. 



ISO SPECIAL ANATOMY OF THE SKELETON 

obtuse angle with the shaft. It is more distinctly marked in the lower half of 
its circumference than in the upper half, where it presents a narrow groove, 
separating tlie head from the tuberosities. Its circumference affords attachment 
to the capsular ligament and is perforated by numerous vascular foramina. 

The Greater Tuberosity (tubercuhim majus). — The greater tuberosity is situated 
on the outer side of the head and lesser tuberosity. Its upper surface is rounded 
and marked by three flat facets, separated by two slight ridges; the highest facet 
gives attachment to the tendon of the Supraspinatus; the middle one, to the Infra- 
spinatus ; the inferior facet and the shaft of the bone below it, to the Teres minor. 
The outer surface of the greater tuberosity is convex, rough, and continuous \\ath 
the outer side of the shaft. 

The Lesser Tuberosity (t'uberculum minus). — The lesser tuberosity is more 
prominent, although smaller than the greater; it is situated in front of the head, 
and is directed inward and forward. Its summit presents a prominent facet 
for the insertion of the tendon of the Subscapularis muscle. The tuberosities 
are separated from each other by a deep groove, the bicipital groove (sulcus inter- 
iuhercularis). This groove lodges the long tendon of the Biceps muscle, accom- 
panied by a branch of the anterior circumflex artery. It commences above be- 
tween the two tuberosities, passes obliquely downward and a little inwai'd, and 
terminates at the junction of the upper with the middle third of the bone. It is 
deep and narrow at the commencement, and becomes shallow and a little broader 
as it descends. In the recent state it is covered with a thin layer of cartilage, 
lined by a prolongation of the synovial membrane of the shoulder-joint, and 
receives the tendon of insertion of the Latissimus dorsi muscle. 

The Shaft (corpus humeri). — The shaft of the humerus is almost cylindrical 
in the upper half of its extent, prismatic and flattened below, and presents three 
borders and three surfaces for examination. 

The anterior border runs from the front of the greater tuberosity above to the 
coronoid depression below, separating the internal from the external surface. 
Its upper part is very prominent and rough, forms the outer Up of the bicipital 
groove, and serves for the attachment of the tendon of the Pectoralis major. 
About its centre it forms the anterior boundary of the rough deltoid impression j 
below, it is smooth and rounded, affording attachment to the Brachialis anticus. 
muscle. 

The external border (iiiargo lateralis) runs from the back part of the greater 
tuberosity to the external condyle, and separates the external from the posterior 
surface. It is rounded and indistinctly marked in its upper half, serving for the 
attachment of the lower part of the insertion of the Teres minor muscle, and below 
this of the external head of the Triceps muscle; its centre is traversed by a broad, 
but shallow, oblique depression, the musculospiral groove (sulcus nervi radialis); 
its lower part is marked by a prominent, rough margin, a little curved from 
behind forward, the external supracondylar ridge, which presents an anterior lip 
for the attachment of the Brachioradialis above and Extensor carpi radialis 
longior below, a posterior lip for the Triceps, and an intermediate space for the 
attachment of the external intermuscular septum. 

The internal border {margo medialis) extends from the lesser tuberosity to the 
internal condyle. Its upper third is marked by a prominent ridge, forming 
the internal lip of the bicipital groove, and gives attachment to the tendon of the 
Teres major. About its centre is an impression for the attachment of the Coraco- 
brachialis, and just below this is seen the entrance of the nutrient canal, directed 
downward. Sometimes there is a second canal situated at the commencement 
of the musculospiral groove, for a nutrient artery derived from the superior pro- 
funda branch of tlie brachial artery. The inferior third of this border is raised 
into a slight ridge, the internal supracondylar ridge, which becomes very prominent 



THE HUMERUS, OR ARM BONE 



181 



below; it presents an anterior lip for the 
attachment of the Brachialis anticus muscle, 
a posterior lip for the internal head of the 
Triceps muscle, and an intermediate space 
for the attachment of the internal intermus- 
cular septum. 

The external surface (fades anterior later- 
alis) is directed outward above, where it is 
smooth, rounded, and covered by the Del- 
toid muscle; forward and outward below, 
where it is slightly concave from above 
downward, and gives origin to part of the 
Brachialis anticus muscle. About the mid- 
dle of this surface is seen a rough, triangular 
impression for the insertion of the Deltoid 
muscle, deltoid impression {tuberositas deltoi- 
dea), a.nd below this the musculospiral groove, 
directed obliquely from behind forward and 
downward, and transmitting the musculo- 
spiral nerve and superior profunda artery. 

The internal surface (fades anterior medi- 
alis), less extensive than the external, is 
directed inward above, forward and inward 
below ; at its upper part it is narrow and 
forms the floor of the bicipital groove; to 
it is attached the Latissimus dorsi. The 
middle part of this surface is slightly 
roughened for the attachment of some of 
the fibres of the tendon of insertion of the 
Coracobrachialis; its lower part is smooth, 
concave from above downward, and gives 
attachment to the Brachialis anticus mus- 
cle.^ A little below the middle of the shaft 
is the nutrient foramen. This leads into a 
nutrient canal, which is directed toward the 
elbow-joint. 

The posterior surface (fades posterior) 
(Fig. 142) appears somewhat twisted, so 
that its upper part is directed a little inward, 
its lower part backward and a little outward. 
Nearly the whole of this surface is covered 
by the external and internal heads of the 



• A sm;ill hook-shaped process of bone, the supracondylar 
process, varying from i/io to 3/4 of an inch in length, is not in- 
frequently found projecting from the inner surface of the 
shaft of the humerus two inches above the internal condyle. 
It is curved downward, forward, and inward, and its 
pointed extremity is connected to the internal border, just 
above the inner condyle, by a ligament or fibrous band, 
which gives origin to a portion of the Pronator teres; through 
the arch completed by this fibrous band the median nerve 
and brachial artery pass when these structures deviate 
from their usual course. Sometimes the nerve alone is 
transmitted through it, or the nerve may be accompanied by 
the ulnar artery in cases of high division of the brachial. A 
well-marked groove is usually found behind the process in 
which the nerve and artery are lodged. This space is anal- 
ogous to the supracondyloid foramen in many animals, and 
probably serves in them to protect the nerve and artery 
from compression during the contraction of the muscles in 
this region. 




Fig. 142. — Left humerus. Posterior surface. 



182 SPECIAL ANATOMY OF THE SKELETON 

Triceps, the former of which is attached to its upper and outer part, the latter to 
its inner and back part, the two being separated by the musculospiral groove. 
The Lower or Distal Extremity is flattened from before backward, and curved 
sHghtly forward; it terminates below in a broad, articular surface which is divided 
into two parts by a slight ridge. Projecting on either side are the external and 
internal condyles. By some anatomists the external condyle is called the external 
epicondyle and the internal condyle is called the internal epicondyle. The articular 
surface extends a little lower than the condyles, and is curved slightly forward, so 
as to occupy the more anterior part of the bone; its greatest breadth is in the 
transverse diameter, and it is obliquely directed, so that its inner extremity occupies 
a lower level than the outer. The outer portion of the articular surface presents 
a smooth, rounded eminence, which has received the name of the capitellum, or 
radial head of the humerus (capitulum humeri) ; it articulates with the cup-shaped 
depression on the head of the radius, and is limited to the front and lower part of 
the bone, not extending as far back as the other portion of the articular surface. 
On the inner side of this eminence is a shallow groove, in which is received the 
inner margin of the head of the radius. Above the front part of the capitellum 
is a slight depression, the radial fossa (fossa radialis), which receives the anterior 
border of the head of the radius when the forearm is flexed. The inner portion 
of the articular surface, the trochlea (trochlea humeri), presents a deep depression 
between two well-marked borders. This surface is convex from before backward, 
concave from side to side, and occupies the anterior, lower, and posterior parts 
of the bone. The external border, less prominent than the internal, corresponds 
to the interval between the radius and the ulna. The internal border is thicker, 
more prominent, and consequently of greater length, than the external. The 
grooved portion of the articular surface fits accurately within the greater sigmoid 
cavity of the ulna; it is broader and deeper on the posterior than on the anterior 
aspect of the bone, and is inclined obliquely from behind forward and from without 
inward. Above the front part of the trochlear surface is seen a smaller depression, 
the coronoid fossa (J'ossa coronoidea), which receives the coronoid process of the 
ulna during flexion of the forearm. Above the back part of the trochlear surface 
is a deep, triangular depression, the olecranon fossa (J'ossa olecrani), in which 
is received the summit of the olecranon process in extension of the forearm. 
These fossae are separated from one another by a thin, transparent lamina of bone, 
which is sometimes perforated by a foramen, the supratrochlear foramen; their 
upper margins afi'ord attachment to the anterior and posterior ligaments of the 
elbow-joint, and they are lined, in the recent state, by the synovial membrane 
of this articulation. The articular surfaces, in the recent state, are covered with 
a thin layer of hyaline cartilage. The external condyle (epicondi/his lateralis) 
is a small, tubercular eminence, less prominent than the internal, curved a little 
forward, and giving attachment to the external lateral ligament of the elbow- 
joint, and to a tendon common to the origin of some of the Extensor and Supinator 
muscles. The internal condyle (epifrochlea or epicondyhis medialis), larger and 
more prominent, is directed a little backward; it gives attachment to the internal 
lateral ligament, to the Pronator teres, and to a tendon common to the origin of 
some of the Flexor muscles of the forearm. The ulnar nerve runs in a groove, 
the ulnar groove (sulcus nervi ulnaris), at the back of the internal condyle, or 
between It and the olecranon process. These condyles are directly continuous 
above with the external and internal supracondylar ridges. 

Structure. — The extremities consist of cancellous tissue, covered with a thin compact layer; 
the shaft is composed of a cylinder of compact tissue, thicker at the centre than at the extremities, 
and hollowed out by a large medullary canal, which extends along its whole length. In the 
head of the humerus the plates of the cancellous tissue are arranged in curves (Fig. 143), 
known as pressure curves. Most of the bone plates are at right angles to the plane of the 



THE HUMERUS, OR ARM BONE 



]S3 



articular surface (the lines of greatest pressure), and they are bound togetlier l)y other bone 
fibres, which usually correspond to the plane of the articulation (the lines of greatest tension). 
This arch-like arrangement strengthens the head of the bone, and it is further strengthened by 
the binding fibres. 

Development. — From eiyht centres (Fig. 144), one for each of the following parts: The 
shaft, head, each tuberosity, the radial head, the trochlear portion of the articular surface, and 
each condyle. The nucleus for the shaft appears near the centre of the bone in the eighth 
week, and soon extends toward the extremities. At birth the humerus is ossified ncarjv in its 
whole length, the extremities remaining cartilaginous. During the first year, sometimes even 
before birth, ossification commences in the head of the bone, and during the third year the centre 
for the greater tuberosity makes its appearance, that for the lesser being small and not appearing 
until tlie fifth year. By the sixth year the centres for the head and tuberosities have increased in 
size and become joined, so as to form a single large epiphysis. 



Epiphyseal line. 



_ > of head and 
tuberosities blend at 
Bth year, and unite 
with shaft at 20th 





Fig. 144. — Plan of the development of the 
humerus from eight centres. 



The lower end of the humerus is developed in the following manner: At the end of the second 
year ossification commences in the capitellum, and from this point extends inward, so as to form 
the chief part of the articular end of the bone, the centre for the inner part of the trochlea not 
appearing until about the age of twelve. Ossification commences in the internal condyle about 
the fifth year, and in the external one not until about the thirteenth or fourteenth year. About 
the sixteenth or seventeenth year the outer condyle and both portions of the articulating surface 
(which have already joined) unite with the shafi ; M \\\r rit^hieenth year the inner condyle l)ecomes 
joined; while the upper epiphysis, although the Hr.s( formed, is not united until about the twen- 
tieth year. 

Articulations. — With the glenoid cavity of the scapula and with the ulna and radius. 

Attachment of Muscles. — To twenty-four — to the greater tuberosity, the Supraspinafus, 
Infraspinatus, and Teres minor; to the lesser tuberosity, the Subscapularis; to the externa! 
bicipital ridge, the Pectoralis major; to the internal bicipital ridge, the Teres major; to the bicip- 
ital groove, the Latissimus dorsi; to the shaft, the Deltoid, Coracobrachialis, Brachialis anticus, 
external and internal heads of the Triceps; to the internal condyle, the Pronator teres, and com- 
mon tendon of the Fle.xor carpi radialis, Palmaris longus. Flexor sublimis digitorum, and Flexor 
carpi ulnaris; to the external, supracondylar ridge, the Brachioradialis and Extensor carpi radi- 



184 SPECIAL ANATOMY OF THE SKELETON 

alls longior; to the external condyle, the common tendon of the Extensor carpi radialis brevior, 
Extensor communis digitorum, Extensor minimi digiti, Extensor carpi ulnaris, and Supinator 
[brevis]; to the back of the external condyle, the Anconeus. 

Surface Form. — The humerus is almost entirely clothed by the muscles which surround it, 
and the only parts of this bone which are strictly subcutaneous are small portions of the inter- 
nal and external condyles. In addition to these, the tuberosities and a part of the head of the 
bone can be felt under the skin and muscles by which they are covered. Of these, the greater 
tuberosity' forms the most prominent bony point of the shoulder, extending beyond the acromion 
process and covered by the Deltoid muscle. It influences materially the surface form of the 
shoulder. It is best felt while the arm is lying loosely by the side; if the arm be raised, it recedes 
from under the finger. The lesser tuberosity, directed forward and inward, is to be felt to the 
inner side of the greater tuberosity, just below the acromioclavicular joint. Between the two 
tuberosities lies the bicipital groove. This can be defined by placing the finger and making 
firm pressure just internal to the greater tuberosity; then, by rotating the humerus, the groove 
will be felt to pass under the finger as the bone is rotated. With the arm abducted from the 
side, by pressing deeply in the axilla the lower part of the head of the bone is to be felt. On 
each side of the elbow-joint, and just above it, the internal and external condyles of the bone 
may be felt. Of these, the internal is the more prominent, but the ridge passing upward from 
it, the internal supracondylar ridge, is much less marked than the external, and, as a rule, is 
not to be felt. Occasionally, however, we find along this border the hook-shaped process men- 
tioned in the foot-note on page 181. The external condyle is most plainly to be seen diu-ing 
semiflexion of the forearm, and its position is indicated by a depression between the attachment 
of the adjacent muscles. From it is to be felt a strong bony ridge running up the outer border 
of the shaft of the bone. This is the external supracondylar ridge; it is concave forward, and 
corresponds with the curved direction of the lower extremity of the humerus. 

Applied Anatomy. — There are several points of surgical interest connected with the humerus. 
First, as regards its development. The upper end, though the first to ossify, is the last to 
join the shaft, and the length of the bone is mainly due to growth from this upper epiphysis. 
Hence, in cases of amputation of the arm in young subjects the humerus continues to grow con- 
siderably, and the end of the bone, which immediately after the operation was covered with a 
thick cushion of soft tissue, begins to project, thinning the soft parts and rendering the stump 
conical. This may necessitate another operation, which consists in the removal of a couple of 
inches or so of the bone, and even after this operation a recurrence of the conical stump may 
take place. 

There are several points of surgical interest in connection with fractures. First, as regards 
their causation, the bone may be broken by direct or indirect violence like the other long bones, 
but, in addition to this, it is probably more frecjuently fractm-ed by muscular action than any 
other of this class of bone in the body. It is usually the shaft, just below the insertion of the 
Deltoid, which is thus broken. Fractures of the upper end may take place through the 
anatomical neck, through the surgical neck, or separation of the greater tuberosity may occur. 
Fracture of the anatomical neck is a very rare accident ; in fact, it is doubted by some whether it 
ever occurs. These fractures are usually considered to be intracapsular, but they are probably 
partly within and partly without the capsule, as the lower part of the capsule is inserted some 
little distance below the anatomical neck, while the upper part is attached to it. They may be 
impacted or nonimpacfed. In most cases there is little or no displacement on account of the 
capsule, in whole or in part, remaining attached to the lower fragment. Separation of the upper 
epiphysis of the humerus sometimes occurs in the young subject, and is marked by a character- 
istic deformity by which the lesion may be at once recognized. This consists in the presence 
of an abrupt projection at the front of the joint a short distance below the coracoid process, 
caused by the upper end of the lower fragment. In fractures of the shaft of the huvterus the 
lesion may take place at any point, but appears to be more common in the lower than in the 
upper part of the bone. The points of interest in connection with these fractures are: (1) That 
the musculospiral nerve may be injured as it lies in the groove on the bone, or may become 
involved in the callus which is subsequently thrown out; and (2) the frequency of nonunion. 
This is believed to be more common in the humerus than in any other bone, and various causes 
have been assigned for it. It would seem most probably to be due to the difiiculty that there 
is in fixing the shoulder-joint and the upper fragment, and possibly the elbow-joint and lower 
fragment also. Other causes which have been assigned for the nonunion are: (1) That in attempt- 
ing passive motion of the elbow-joint to overcome any rigidity which may exist, the movement 
does not take place at the articulation, but at the seat of fracture; or that the patient, in con- 
sequence of the rigidity of the elbow, in attempting to flex or extend the forearm moves the 
fragment and not the joint. (2) The presence of small portions of muscle tissue between the 
broken ends. (3) Want of support to the elbow, so that the weight of the arm tends to drag the 
lower fragment away from the upper. An important distinction to make in fractures of the 
loiver end of the humerus is between those that involve the elbow-joint and those which do not; 
the former are always serious, as they may lead to stiffness of the joint and impairment of the 



THE ULNA, Oli ELBOW BONE 185 

utility of the limb. They include the T-shaped fracture and oblique fractures which involve 
the articular surface. The fractures which do not involve the joint are the transverse above 
the condyles and the so-called epitrochlear fracture, in which the tip of the internal condyle 
is broken off, genei-ally by direct violence. 

Under the head of i-eparation of the lower epiphysis two separate injuries have been described: 
(1) Where the whole of the four ossific centres which form the lower extremity of the bone 
are separated from the shaft; and (2) where the articular portion is alone separated, the two 
condyles remaining attached to the shaft of -the bone. The epiphyseal line between the shaft 
and lower end runs across the bone just above the tips of the condyles, a point to be borne in 
mind in performing the operation of excision. Shortening may follow epiphysitis. 

Tumors originating from the humerus are of frequent occurrence. A not uncommon place 
for a chondroma to grow from is the shaft of the bone somewhere in the neighborhood of the 
insertion of the deltoid. Sarcomata frequently grow from this bone. 



THE FOREARM. 

The forearm is that portion of the upper extremity which is situated between 
tlie elbow and the wrist. Its skeleton is composed of two bones, the ulna and 
radius. 

The Ulna, or Elbow Bone (Figs. 14-5, 147). 

The ulna is a long bone, prismatic in form, placed at the inner side. of the 
forearm, parallel with the radius. It is the larger and longer of the two bones. 
Its upper extremity, of great thickness and strength, forms a large part of the 
articulation of the elbow-joint; it diminishes in size from above downward, its 
lower extremity being very small, and excluded from the wrist-joint by the inter- 
position of an intra-articular fibrocartilage. It is divisible into a shaft and two 
extremities. 

The Upper or Proximal Extremity, the strongest part of the bone, presents 
for examination two large, curved processes, the olecranon process and the 
coronoid process; and two concave, articular cavities, the greater and lesser 
sigmoid cavities. 

The olecranon process {i •lecranon) is a large, thick, curved eminence situated 
at the upper and back part of the ulna. It is curved forward at the summit 
so as to present a prominent tip which is received into the olecranon fossa of the 
humerus in extension of the forearm, its base being contracted where it joins the 
shaft. This is the narrowest part of the upper end of the ulna. The posterior 
surface of the olecranon, directed backward, is triangular, smooth, subcutaneous, 
and covered by a bursa. Its zipper surface is of a quadrilateral form, marked 
behind by a rough impression for the attachment of the Triceps muscle; and in 
front, near the margin, by a slight transverse groove for the attachment of part 
of the posterior ligament of the elbow-joint. Its anterior surface is smooth, 
concave, covered with cartilage in the recent state, and forms the upper and 
back part of the greater sigmoid cavity. The lateral borders present a continuation 
' of the same groove that was seen on the margin of the superior surface ; they serve 
for the attachment of ligaments — viz., the back part of the internal lateral ligament 
internally, the posterior ligament externally. To the inner border is also attached 
a part of the Flexor carpi ulnaris, while to the outer border is attached the Anconeus 
muscle. 

The coronoid process {processus coronoideus) is a triangular eminence of bone 
which projects horizontally forward from the upper and front part of the ulna. 
Its base is continuous with the shaft, and of considerable strength; so much so 
that fracture of it is an accident of rare occurrence. Its apex is pointed, slightly 
curved upward, and is received into the coronoid depression of the hiuneriis in 



186 



SPECIAL ANATOMY OF THE SKELETON 

Ulna. 



, cr a>i 



'C^imiiar ligamtnt. 
Radius. 



PRONATOR TERES 



Occasional ongm of y. . . ^r 

rUEXOR tONQUS POLL CIS *' / \ \ 

V 1 \ I 



Radial origin of flexor 

DIGITORUM 




Oapstdar 



Styloid pi ocess 



Styloid process. 
Fig. 145, — Bones of the left forearm, Antei'ior view. 



THE ULNA, OB ELBOW BONE 



187 



Olecranon process 

\ 



flexion of the forearm. Its upper surface is smooth, concave, and forms the lower 
part of the greater sigmoid cavity. The under siirface is concave; and marked by 
an impression internally for the insertion of the Brachialis anticus. At the junc- 
tion of this surface with the shaft is a rough eminence, the tubercle of the ulna 
(tuberositas ulnae), for the attachment of the oblique ligament of the middle 
radio-ulnar articulation. Its outer surface presents' a narrow, oblong, articular 
depression, the lesser sigmoid cavity. The inner surface, by its prominent 
free margin, serves for the attachment of part of the internal lateral ligament. 
At the front part of this surface is a small, rounded eminence for the attach- 
ment of one head of the Flexor sublimis digitorum; behind the eminence, a 
depression for part of the origin of the Flexor profundus digitorum; and, descend- 
ing from the eminence, a ridge which gives attachment to one head of the Pro- 
nator teres. Generally, the Flexor longus pollicis has an origin from the lower 
part of the coronoid process by a rounded bundle of muscle fibres. 

The greater sigmoid cavity (incisura semilunaris) is a semilunar depression 
of large size, formed by the olecranon and coronoid processes, and serving for 
articulation with the trochlear surface of the 
humerus. About the middle of either lateral 
border of this cavity is a notch which con- 
tracts it somewhat, and serves to indicate 
the junction of the two processes of which 
it is formed. The cavity is concave from 
above downward, and divided into two 
lateral parts by a smooth, elevated ridge 
which runs from the summit of the olecranon 
to the tip of the coronoid process. Of these 
two portions, the internal is the larger, and 
is slightly concave transversely; the external 
portion is convex above, slightly concave be- 
low. The articular surface, in the recent 
state, is covered with a thin layer of hyaline 
cartilage. 

The lesser sigmoid cavity {incisura radi- 
alis) is a narrow, oblong, articular depres- 
sion, placed on the outer side of the coronoid 
process, and receives the lateral articular sur- 
face of the head of the radius. It is concave 
from before backward, and its extremities, 
which are prominent, serve for the attach- 
ment of the orbicular ligament. In the recent state it is covered with a thin layer 
of hyaline cartilage. 

The Shaft (corpus ulnae), at its upper part, is prismatic in form, and curved 
from behind forward and from without inward, so as to be convex behind and 
externally; its central part is quite straight; its lower part rounded, smooth, and 
bent a little outward; it tapers gradually from above downward, and presents 
for examination three borders and three surfaces. 

The anterior or palmar border (marcjo volaris) commences above at the prominent 
inner angle of the coronoid process, and terminates below in front of the styloid 
process. It is well marked above, smooth and rounded in the middle of its extent,' 
and affords origin to the Flexor profundus digitorum; its lower fourth, marked 
off from the rest of the border by the commencement of an oblique ridge on the 
anterior surface, serves for the origin of the Pronator quadratus. It separates 
the anterior from the internal surface. 

The posterior or dorsal border (margo dorsalis) commences above at the apex 
of the triangular subcutaneous surface at the back part of the olecranon, and 




188 



SPECIAL ANATOMY OF THE SKELETON 

Ulna. 



Capsular ligament 




LIMIS DIGITORUM, 



■Capsular ligament 



Fig. 147. — Bones of the left forearm. Posterior view. 



THE ULNA, OR ELBO W BONE 1,S9 

terminates below at the back part of the styloid process; it is well marked in the 
upper three-fourths, and gives origin to the aponeurosis common to the Flexor 
carpi ulnaris, the Extensor carpi ulnaris, and the Flexor profundus digitonim 
muscles; its lower fourth is smooth and rounded. This border separates the 
internal from the posterior surface. 

The external or interosseous border (crista interossea) commences above by the 
union of two lines, which converge one from each extremity of the lesser sigmoid 
cavity, enclosing between them a triangular space for the origin of part of the 
Supinator [brevis], and terminates below at the middle of the. lower extremity. 
Its two middle fourths are very prominent; its lower fourth is smooth and rounded. 
This border gives attachment to the interosseous membrane, and .separates the 
anterior from the posterior surface. 

The anterior or palmar surface {fades volaris') lies between the anterior and 
external borders, is much broader above than below, is concave in the upper three- 
fourths of its extent, and affords origin to the Plexor profundus digitorum; its 
lower fourth, also concave, is covered by the Pronator quadratus. The lower 
fourth is separated from the remaining portion of the bone by a prominent 
ridge (pronator ridge) directed obliquely from above downward and inward; 
this ridge marks the extent of attachment of the Pronator quadratus. At the 
junction of the upper with the middle third of the bone is the nutrient foramen. 
It opens into the nutrient canal, which is directed obliquely inward and upward 
(proximally). 

The posterior or extensor surface (fades dorsalis) is bounded externally 
by the interosseous border, internally by the posterior border, and is directed 
backward and outward; it is broad and concave above, somewhat narrower and 
convex in the middle of its course, narrow, smooth, and rounded below. It pre- 
sents, above, an oblique ridge, which runs from the posterior extremity of the 
lesser sigmoid cavity, downward to the posterior border; the triangular surface 
above this ridge receives the insertion of the Anconeus muscle, while the upper 
part of the ridge itself aiYords origin to the Supinator. The surface of bone 
below this is subdivided by a longitudinal ridge into two parts; the internal part 
is smooth, and covered by the Extensor carpi ulnaris; the external portion, wider 
and rougher, gives origin from above downward to part of the Supinator, the 
Extensor ossis metacarpi pollicis, the Extensor longus pollicis, and the Extensor 
indicis muscles. 

The internal surface (Jades medialis) is broad and concave above, narrow and 
convex below. It gives origin by its upper three-fourths to the Flexor profundus 
digitorum muscle; its lower fourth is subcutaneous. The anterior and the inner 
surfaces constitute the flexor surface. 

The Distal or Lower Extremity is of small size, and excluded from the 
articulation of the wrist-joint. It presents for examination two eminences, tlie 
outer and larger of which is a rounded, articular eminence, termed the head 
(capitulum ulnae), the inner, narrower and more projecting, is a nonarticular 
eminence, the styloid process (processus sti/loideus). The head presents an 
articular facet, part of which, of an oval form, is directed downward, and plays 
on the upper surface of the triangular fibrocartilage which separates it from the 
wrist-joint; the remaining portion, directed outward, is narrow, convex, and 
received into the sigmoid cavity of the radius. The styloid process projects from 
the inner and back part of the bone, and descends a little lower than the head, 
terminating in a rounded summit, which affords attachment to the internal lateral 
ligament of the wrist. The head is separated from the styloid process by a 
depression for the attachment of the triangular intra-articular fibrocartilage; and 
behind, by a shallow groove for the passage of the tendon of the Extensor carpi 
ulnaris. 



190 



SPECIAL ANATOMY OF THE SKELETON 



Appears at^^ 
10th year. 



Olecranon. 



-Joins shaft a 
16th year. 



Stracture. — Similar to tliat of the other long bones. 

Development. — From thrive centres — one for the shaft, one for the inferior extremity, and 
one for the olecranon (Fig. 148). Ossification commences near the middle of the shaft about 
the eighth week, and soon extends through the greater part of the bone. At birth the ends are 
cartilaginous. About the fourth year a separate osseous nucleus appears in the middle of the 
head, which soon extends into the styloid process. About the tenth year ossific material appears 
in the olecranon near its extremity, the chief part of this process being formed from an extension 
of the shaft of the bone into it. At about the sixteenth year the upper epiphysis becomes joined 
to the shaft, and at about the twentieth year the lower one. 
Articulations. — With the humerus and radius. 

Attachment of Muscles. — To sixteen: To the olecranon, the Triceps, Anconeus, and one 
head of the Flexor carpi ulnaris. To the coronoid process, the Brachialis anticus. Pronator teres. 
Flexor sublimis digitorum, and Flexor profundus digitorum; 
generally also the Flexor longus pollicis. To the shaft, the 
Flexor profundus digitorum, Pronator quadratus, Flexor carpi 
ulnaris. Extensor carpi ulnaris. Anconeus, Supinator [brevis], 
Extensor ossis metacarpi pollicis. Extensor longus pollicis, and 
Extensor indicis. 

Surface Form. — The most prominent part of the ulna on 
the surface of the body is the olecranon process, which can 
always be felt at the back of the elbow-joint. When the fore- 
arm is flexed, the upper quadrilateral surface can be felt, 
directed backward; during extension it recedes into the olec- 
ranon fossa, and the contracting fibres of the triceps prevent 
its being perceived. At the back of the olecranon is the 
smooth, triangular, subcutaneous surface, which below is 
continuous with the posterior border of the shaft of the bone, 
and felt in every position of the forearm. During extension 
the upper border of the olecranon is slightly above the level 
of the internal condyle, and the process itself is nearer to this 
condyle than the outer one. Running down the back of the 
forearm, from the apex of the triangular surface which forms 
the posterior surface of the olecranon, is a prominent ridge of 
bone, the posterior border of the ulna. This may be felt 
throughout the entire length of the shaft of the bone, from the 
olecranon above to the styloid process below. As it passes 
down the forearm it pursues a sinuous course and inclines to 
the inner side, so that, though it is situated in the middle of 
the back of the limb above, it is on the inner side of the wrist 
at its termination. It becomes rounded off in its lower third, 
and may be traced below to the small, subcutaneous surface of 
the st3'loid process. Internal to this border the lower fourth 
of the inner surface ma)' be felt. The styloid process may be 
felt as a prominent tubercle of bone, continuous above with the posterior subcutaneous border 
of the ulna, and terminating below in a blunt apex, which lies a little internal and behind, but 
on a level with, the wrist-joint. The styloid process is best felt when the hand is in the same 
line as the bones of the forearm, and in a position midway between supination and pronation. 
If the forearm is pronated while the finger is placed on the process, it will be felt to recede, and 
another prominence of bone will appear just behind and above it. This is the head of the ulna, 
which articulates with thejower end of the radius and the triangular intra-articular fibrocarti- 
lage, and now projects between the tendons of the Extensor carpi ulnaris and the Extensor 
minimi dij;iti muscles. 



8th' ^ 



Appears aij 
Jfth year. 



^Joins shaft at 
Both year. 



Inferior extremity. 

Fig, 148. — Plan of the development 
of the ulna. From three centres. 



The Radius. 

The radius is situated on the outer side of the forearm, lying side by side with the 
ulna, which exceeds it in length and size (Fig. 145). Its upper end is small, and 
forms only a small part of the elbow-joint; but its lower end is large, and forms 
the chief part of the wrist. It is one of the long bones, prismatic in form, slightly 
curved longitudinally, and, like other long bones, has a shaft and two extremities. 

The Proximal or Upper Extremity presents a head, neck, and tuberosity. 

The head (capituluni radii) is of a cylindrical form, depressed on its upper 
surface into a shallow cup (fovea capituli radii), which articulates with the capitel- 
lum or radial head of the humerus. In the recent state it is covered with a layer 



THE RADIUS 191 

of hyaline cartilage which is thinnest at its centre. Around the circumference of 
the head is a smooth, articular surface {circumferentia articularis) , broad internally, 
where it articulates with the lesser sigmoid cavity of the ulna; narrow in the rest 
of its circumference, where it rotates within the orbicular ligament. It is coated 
with hyaline cartilage in the recent state. The head is supported on a round, 
smooth, and constricted portion of bone, called the neck (collum radii), which 
presents, behind, a slight ridge, for the attachment of part of the Supinator 
[brevis]. Beneath the neck, at the inner and front aspect of the bone, is a rough 
eminence, the bicipital tuberosity {tuberositas radii). Its surface is divided into 
two parts by a vertical line — a posterior, rough portion, for the insertion of the 
tendon of the Biceps muscle; and an anterior, smooth portion, on which a bursa 
is interposed between the tendon and the bone. 

The Shaft {corpus radii) is prismoid in form, narrower above than below, and 
slightly curved, so as to be convex outward. It presents three surfaces, separated 
by three borders. 

The anterior border {marcjo volaris) extends from the lower part of the tuber- 
osity above to the anterior part of the base of the styloid process below. It 
separates the anterior from the external surface. Its upper third is very promi- 
nent; and from its oblique direction, downward and outward, has received the 
name of the oblique line of the radius. It gives insertion externally at the 
Supinator [brevis] internally, it limits the origin of the Flexor longus pollicis, and 
between these, arising from it, is the radial origin of the Flexor sublimis digitorum. 
The middle third of the anterior border is indistinct and rounded. Its lower 
fourth is sharp, prominent, affords attachment to the Pronator quadratus and to the 
posterior annular ligament of the wrist, and terminates in a small tubercle at the 
base of the styloid process, into which is inserted the tendon of the Brachioradialis. 

The posterior border {margo dorsalis) commences above at the back part of 
the neck of the radius, and terminates below at the posterior part of the base of 
the styloid process; it separates the posterior from the external surface. It is 
indistinct above and below, but well marked in the middle third of the bone. 

The internal border {crista interossea) commences above at the back part of 
the tuberosity, where it is rounded and indistinct, becomes sharp and prominent 
as it descends, and at its lower part divides into two ridges, which descend to 
the anterior and posterior margins of the sigmoid cavity. This border separates 
the anterior from the posterior surface, and has the interosseous membrane 
attached to it throughout the greater part of its extent. 

The anterior or flexor surface {fades volaris) is concave for its upper three- 
fourths, and gives origin to the Flexor longus pollicis muscle; it is broad and flat 
for its lower fourth, and gives attachment to the Pronator quadratus. A promi- 
Bent ridge limits the attachment of the Pronator quadratus below, and between 
this and the inferior border is a triangular rough surface for the attachment of 
the anterior ligament of the wrist-joint. At the junction of the upper and middle 
third of this surface is the nutrient foramen, the opening of the nutrient canal, 
which is directed obliquely upward (proximally). 

The posterior or extensor surface {fades dorsalis) is rounded, convex, and 
smooth in the upper third of its extent, and covered by the Supinator [brevis] 
muscle. Its middle third is broad, slightly concave, and gives origin to the 
Extensor ossis metacarpi pollicis above, the Extensor brevis pollicis below. Its 
lower third is broad, convex, and covered by the tendons of the muscles, which 
subsequently run in the grooves on the lower end of the bone. 

The external surface {fades lateralis) is rounded and convex throughout its 
entire extent. Its upper third gives attachment to the Supinator [brevis] muscle. 
About its centre is seen a rough ridge, for the insertion of the Pronator teres 
muscle. Its lower part is narrow, and covered by the tendons of the Extensor 
ossis metacarpi pollicis and Extensor brevis pollicis muscles. 



192 SPECIAL ANATOMY OF THE SKELETON 

The Lower Extremity is large, of. quadrilateral form, and provided with two 
articular surfaces — one at the extremity, for articulation with the carpus, and one 
at the inner side of the bone, for articulation with the ulna. The carpal articular 
surface (fades articularis carpea) is of triangular form, concave, smooth, and divided 
by a slight antero-posterior ridge into two parts. Of these, the external is of a tri- 
angular form, and articulates with the scaphoid bone; the inner is quadrilateral 
and articulates with the semilunar bone. The articular surface for the head of the 
ulna is called the sigmoid cavity of the radius (incisura ulnaris) ; it is narrow, con- 
cave, smooth, and articulates with the head of the ulna. The circumference of this 
end of the bone presents three surfaces — an anterior, external, and posterior. The 
anterior surface, rough and irregular, affords attachment to the anterior ligament of 
the wrist-joint. The external surface is prolonged obliquely downward into a strong 
conical projection, the styloid process (processus styloideus), which gives attachment 
by its base to the tendon of the Brachioradialis, and by its apex to the external 
lateral ligament of the wrist-joint. The outer surface of this process is marked 
by a flat gi-oove, which runs obliquely downward and forward, and gives passage 
to the tendons of the Extensor ossis metacarpi pollicis and the Extensor brevis 
pollicis. The posterior surface is convex, affords attachment to the posterior 
ligament of the wrist, and is marked by three grooves. Proceeding from without 
inward, the first groove is broad but shallow, and subdivided into two by a slightly 
elevated ridge; the outer of these two transmits the tendon of the Extensor carpi 
radial is longior, the inner the tendon of the Extensor carpi radialis brevior. The 
second, which is near the centre of the bone, is a deep but narrow groove, bounded 
on its outer side by a sharply defined ridge; it is directed obliquely from above, 
downward and outward, and transmits the tendon of the Extensor longus pollicis. 
The third, lying most internally, is a broad groove, for the passage of the tendons 
of the Extensor indicis and Extensor communis digitorum. 

Structure. — Similar to that of the other long bones. 

Development (Fig. 149). — From three centres, one for the shaft and 07ie for each extremity. 
That for the shaft makes its appearance near the centre of the bone, about the eighth week of 
fetal life. About the end of the second year ossification commences in the lower epiphysis, and 
about the fifth year in the upper end. At the age of seventeen or eighteen the upper epiphysis 
becomes joined to the shaft, the lower epiphysis becoming united about the twentieth year. Some- 
times an additional centre appears about the fourteenth year in the bicipital tuberosity. 

Articulation. — With four bones — the humerus, idna, scaphoid, and semilunar. 

Attachment of Muscles. — To nitie: To the tuberosity, the Biceps; to the oblique ridge, the 
Supinator [brevis], Flexor sublimis digitorum, and Flexor longus pollicis; to the shaft (its anterior 
surface), the Flexor longus pollicis and Pronator quadratus; (its posterior surface), the Extensor 
ossis metacarpi pollicis and Extensor brevis pollicis; (its outer surface), the Pronator teres; and 
to the styloid process, the Brachioradialis. 

Surface Form. — Just below and a little in front of the posterior surface of the external con- 
dyle a part of the head of the radius may be felt, covered by the orbicular and external lateral 
ligaments. There is in this situation a little dimple in the skin, which is most visible when the 
arm is extended, and which marks the position of the head of the bone. If the finger is placed 
on this dimple and the forearm pronated and supinated, the head of the bone will he distinctly 
perceived rotating in the lesser sigmoid cavity. The upper half of the shaft of the radius can- 
not be felt, as it is sturounded by the fleshy muscles arising from the external condyle. The 
lower half of the shaft can be readily examined, although covered by tendons and muscles and 
not strictly subcutaneous. If traced downward, the shaft will be felt to terminate in a lozenge- 
shaped, convex surface on the outer side of the base of the styloid process. This is the only 
subcutaneous part of the bone, and from its lower extremity the apex of the styloid process 
will be felt bending inward toward the wrist. About the middle of the posterior aspect of the 
lower extremity of the bone is a well-marked ridge, best perceived when the hand is slightly 
flexed on the A\Tist. It forms the outer boundary of the oblique groove on the posterior surface 
of the bone, through which the tendon of the Extensor longus pollicis runs, and serves to keep 
that tendon in place. 

Applied Anatomy of the Radius and Ulna. — The two bones of the forearm are more often 
broken together than is either the radius or ulna separately. It is, therefore, convenient to consider 
fractures of both bones in the first instance, and subsequently to mention the principal fractures 



THE RADIUS 



193 



Apyears a 
5th year. 



Unites with shaft 
- about 18th or 
20th year. 



which take place in each bone individually. These fractures may be produced bv either direct 
or indirect violence, though more commonly by direct violence. When indirect force i.s ap|)lied 
to the forearm the radius generally alone gives way, though both bones may suffer. The fracture 
from indirect force generally takes place somewhere about the middle of the bones; fracture 
from direct violence may occur at any part, more often, however, in the lower half of the bone. 
The fracture is usually transverse, but may be more or less oblique. A point of interest in con- 
nection with these fi-actures is the tendency that there is for the two bones to unite across the 
interosseous membrane; the limb should therefore be put up in a position midway between supi- 
nation and pronation, which is not only the most comfortable position, but also separates the bone-s 
most widely from each other, and therefore diminishes 
the risk of the bones becoming united across the inter- 
osseous membrane. The splints, anterior and posterior, 
which are applied in these cases should be rather wider 
than the limb, so as to prevent any lateral pressure on 
the bones. In these cases there is a greater liability to 
gangrene from the pressure of the splints than in other 
parts of the body. This is no doubt due princijially to 
two causes: (1) The flexion of the forearm compressing 
to a certain extent the brachial artery and retarding 
the flow of blood to the limb; and (2) the superficial 
position of the two main arteries of the forearm in a 
part of their course, and their liability to be compressed 
by the splints. The special fractures of the ulna are: 

(1) Fracture of the olecranon. This may be caused by 
direct violence, falls on the elbow with .the forearm 
flexed, or by muscular action by the sudden contraction 
of the triceps. The most common place for the frac- 
ture to occur is at the constricted portion where the 
olecranon joins the shaft of the bone, and the fracture 
may be either transverse or oblique; but any part may 
be broken, even a thin shell may be torn off. Fractures 
from direct violence are occasionally comminuted. The 
displacement is sometimes very slight, owing to the 
fibrous structures around the process not being torn. 

(2) Fracture of the coronoid process sometimes occurs 
as a complication of dislocation backward of the bones 
of the forearm, but it is doubtful if it ever occurs as an 
xmcomplicated injury. (3) Fractures of the shaft of the 
ulna may occur at any part, but usually takes place at the 
middle of the bone or a little below it. They are usually 
the result of direct violence. (4) The styloid process may be knocked off by direct violence. 
Fractures of the radius consist of: (1) Fracture of the head of the bone; this generally occurs 
in conjunction with some other lesion, but may occur as an uncomplicated injury. (2) Fracture 
of the neck may also take place, but is generally complicated with other injury. (3) Fractures of 
the shaft of the radius are very common, and may take place at any part of the bone. They 
may take place from either direct or indirect violence. In fractures of the upper third of the 
shaft of the bone, that is to say, above the insertion of the Pronator teres, the displacement is 
very great. The upper fragment is strongly supinated by the Biceps and Supinator, and flexed 
by the Biceps, while the lower fragment is pronated and drawn toward the ulna by the two 
pronators. If such a fracture is put up in the ordinary position, midway between supination 
and pronation, the fracture will unite with the upper fragment in a position of supination, and 
the lower one in the mid-position, and thus considerable impairment of the movements of the 
hand will result. The limb should be put up with the forearm supinated. (4) The most impor- 
tant fracture of the radius is that of the lower end (Colles' fracture). The fracture is transverse, 
and generally takes place about an inch from the lower extremity. It is caused by falls on the 
]5alm of the hand, and is an injury of advanced life, occurring more frequently in the female 
than the male. In consequence of the manner in which the fracture is caused, the upper frag- 
ment becomes driven into the lower, and impaction is the result; or else the lower fragment 
becomes split up into two or more pieces, so that no fixation occurs. Separation of the lower 
epiphysis of the radius may take place in the young. This injury and Colles' fracture may be 
distinguished from other injuries in this neighborhood — especially dislocation, with W'hich it is 
liable to be confounded — by observing the relative positions of the styloid processes of the ulna 
and radius. In the natural condition of parts, with the arm hanging by the side, the styloid 
process of the radius is on a lower level than that of the ulna; that is to say, nearer the groiuid. 
After fracture or separation of the epiphysis this process is on the same or a higher level than that 
of the ulna, whereas it would be unaltered in position in dislocation. 

13 



.ippeari 
2d yea I 



Unites with shaft 
about 20th year. 



Lowei extiemity. 



194 



SPECIAL ANATOMY OF THE SKELETON 



THE HAND, 

The skeleton of the hand is subdivided into three segments — the carpus, or wrist 
bones; the metacarpus, or bones of the palm; and the phalanges, or bones of the digits. 




FLEXOR 

^ PROFUNDUS 
f I DIGITORUM 



Fio. 150. — Bones of the left hand. Palmar surface. 



THE CARPUS 



195 



The Carpus (Ossa Carpi) (Figs. 150, 151). 

The bones of the carpus, eight in number, are arranged in two rows. Those 
of the upper row, enumerated from the radial to the uhiar side, are the scaphoid. 



'-^Aj^a 




EXTENSOR COMMUNIS 

DiGiTORUM and 

EXTENSOR INDICIS. 



Fig. 151.— Bonea of the left hand. Dorsal surface. 



196 



SPECIAL ANATOMY OF THE SKELETON 



semilunar, cuneiform, and pisiform; those of the lower row, enumerated in the 
same order, are the trapezium, trapezoid, os magnum, and unciform. 

Common Characters of the Carpal Bones. — Each bone (excepting the pisi- 
form) presents six surfaces. Of these the anterior, palmar, or volar, and the 
posterior or dorsal are rough for hgamentous attachment, the dorsal surface being 
the broader, except in the scaphoid and semilunar. The superior or proximal 
and inferior or distal are articular, the superior generally convex, the inferior 
concave; and the internal and external are also articular when in contact with 
contiguous bones, otherwise rough and tubercular. The structure of all is similar, 
consisting of cancellous tissue enclosed in a layer of compact bone. 




Vad'^'' 



With 1 
Fig. 152. — Diagram to show articulations 



Bones of the Upper Row. — The scaphoid or navicular bone {os naviculare 
manus) (Fig. 1.5.3) is the largest bone of the first row. It is situated at the upper 
and outer part of the carpus, its long axis being from above downward, outward, 
and forward. 



For radius 



For semilunar 



Tuberosity 



For trapesimn 





For OS magnum. 



tor f)apezoid 

A B 

Fig. 153. — The left scaphoid. A, seen from behind; B, seen from in front. 

Surfaces. — The superior surface is convex, smooth, of triangular shape, and 
articulates with the lower end of the radius. The inferior surface, directed down- 
ward, outward, and back\i'ard, is smooth, convex, also triangular, and divided by 
a slight ridge into two parts, the external of which articulates with the trapezium, 
the inner with the trapezoid. The posterior or dorsal surface presents a narrow, 
rough groove which runs the entire length of tlie bone and serves for the attachment 
of ligaments. The anterior or palmar siu-face is concave above, and elevated at 
its lower and outer part into a prominent rounded tuberosity (tuberculum ossis 
iiavicidaris), which projects forward from the front of the carpus and gives attach' 



THE CARPUS 



197 



ment to the anterior annular ligament of the wrist and sometimes a few fibres 
of the Abductor poUicis. The external surface is rough and narrow, and gives 
attachment to the external lateral ligament of the wrist. The internal surface 
presents two articular facets; of these, the superior or smaller one is flattened, 
of semilunar form, and articulates with the semilunar; the inferior or laro-er is 
concave, forming, with the semilunar bone, a concavity for the head of the os 
magnum. 

To ascertain to which side the bone belongs, hold the convex radial articular surface upward, 
and the dorsal surface backward; the prominent tubercle will be directed to the side to which 
the bone belongs. 

Articulations. — With five bones — the radius above, trapezium and trapezoid l)elo\v, os 
magnum and semilunar internally. 

Attachment of Muscles. — Occasionally a few fibres of the Abductor pollicis. 

The semilunar bone (Fig. 154) may be distinguished by its deep concavity and 
crescentic outline. It is situated in the centre of the upper row of the carpus, 
between the scaphoid and cuneiform. 



For cuneiform 





For scaphoid 
For unciform For os magnum 

A B 

Fig. 154. — The left semilunar. A, anterior and internal surfaces; B, external surface. 

Surfaces. — The superior surface, convex, smooth, and bounded by four edges, 
articulates with the radius. The inferior surface is deeply concave, and of greater 
extent from before backward than transver,sely ; it articulates with the head of the 
OS magnum and by a long, narrow facet (separated by a ridge from the general 
surface) with the unciform bonc^^fhe anterior or palmar and posterior or dorsal 
surfaces are rough, for the attachment of ligaments, the former being the broader 
and of a somewhat rounded form. The external surface presertts a narrow, flat- 
tened, semilunar facet for articulation with the scaphoid. The internal surface 
js marked by a smooth, quadrilateral facet, for articulation with the cuneiform. 

To ascertain to which hand this bone belongs, hold it with the dorsal surface upward, and 
the convex articular surface backward; the quadrilateral articular facet will then point to the 
side to which the bone belongs. 

Articulations. — With five bones — the radius above, os magnum and unciform below, sca])hoid 
externally, and cuneiform internally. 



For pisifor 




The cuneiform (os f.riquetrum) (Fig. 155) may be 
distinguished by its pyramidal shape, and by 'its 
having an oval, isolated facet for articulation with the 
pisiform bone. It is situated at the upper and inner 
side of the carpus. 

Surfaces. — ^The superior surface presents an internal, 
i'ough, nonarticular portion, and an external or 
articular portion, which is convex, smooth, and articu- 
lates with the triangular intra-articular fibrocartilage 
of the wrist. The inferior surface, directed outward, is concave, sinuously curved, 
and smooth for articulation with the unciform. The posterior or dorsal surface is 



For unciform 
Fig. 155. — The left cuneiform. 



198 SPECIAL ANATOMY OF THE SKELETON 

rough, for the attachment of ligaments. The anterior or palmar surface presents. 
at its inner side, an oval facet, for articulation with the pisiform, and is rough 
externally, for ligamentous attachment. The external surface, the base of the 
pyramid, is marked by a flat, quadrilateral, smooth facet, for articulation with 
the semilunar. The internal surface, the summit of the pyramid, is pointed and 
roughened, for the attachment of the internal lateral ligament of the wrist. 

To ascertain to which hand this bone belongs, hold it so that the base is directed backward, 
and the articular facet for the pisiform bone upward; the concave articular facet will point to 
the side to which the bone belongs. 

Articulations. — With three bones — the semilunar externally, the pisiform in front, the unci- 
form below; and with the triangular, interarticular fibrocartilage which separates it from the 
lower end of the ulna. 

The pisiform (os pisiforme) (Fig. 156) may be known by its small size and by 

its presenting a single articular facet. It is situated on a plane anterior to the 

other bones of the carpus; it is spheroidal in form, with its long 

For cuneiform ,. , ,. , , j.- n 

, ' diameter directed vertically. 

Surfaces. — Its posterior surface is a smooth, oval facet, for 

articulation with the cuneiform. This facet approaches the 

superior, but not the inferior border of the bone. The anterior 

Fig. 156.— The left or palmar surface is rounded and rough, and gives attachment to 

posterior and lateral the anterior annular ligament and to the Flexor carpi ulnaris 

sur aces. ^^^ Origin to the Abductor minimi digiti. The outer and inner 

surfaces are also rough, the former being concave, the latter usually convex. 

To ascertain to which hand this bone belongs, hold the bone with its posterior or articular 
facet downward and the nonarticular portion of the same surface backward; the inner concave 
surface will point to the side to which it belongs. 

Articulations. — With one bone, the cuneiform. 

Attachment of Muscles. — To two — the Flexor carpi ulnaris and Abductor minimi digiti; 
and to the anterior annular ligament. 

Bones of the Lower Row. — The trapezium (os multangtdum majus) (Fig. 
157) is of very irregular form. It may be distinguished by a deep groove, for 
the tendon of the Flexor carpi radialis muscle. It is situated at the external and 
inferior part of the carpus between the scaphoid and first metacarpal bone. 

For scaphoid 

For trapezoid ^,.r». / ,-5;:^^?>C n ± -j 

■^ , . — -^"^Ss. / .^i^'-- «^ For trapezoid 




For 2nd Al-.M 
metacarpal ^ ' '^ 




Bidge 




\ 
For 1st metacarpal F°^ ^'«^ metacarpal 

A B 

Fig. 157. — The left trapezium. A, as seen from in front; B, from above and mesal side. 

Surfaces. — The superior surface, concave and smooth, is directed upward and 
inward, and articulates with the scaphoid. The inferior surface, directed down- 
ward and inward, is oval, concave from side to side, convex from before backward, 
so as to form a saddle-shaped surface, for articulation with the base of the first 
metacarpal bone. The anterior or palmar surface is narrow and rough. At its 
upper part is a deep groove running from above obliquely downward and inward; 
it transmits the tendon of the Flexor carpi radialis, and is bounded externally 



THE CARPUS 199 

by a prominent ridge, the oblique ridge of the trapezium {hiherruluni ossis mul- 
tanguli majoris). This surface gives origin to the Abductor pollicis, Opponens 
poUicis, sometimes to a portion of the superficial head of the Flexor bre\-is pollicis 
muscles, and the anterior annular ligament. The posterior or dorsal surface 
is rough. The external surface is also broad and rough, for the attachment of 
ligaments. The internal surface presents two articular facets; the upper one, 
large and concave, articulates with the trapezoid; the lower one, small and oval, 
with the base of the second metacarpal bone. 

To ascertain to which hand this bone belongs, hold it with the grooved palmar surface upward, 
and the external broad, nonarticular surface backward; the saddle-shaped surface will then be 
directed to the side to w-hich the bone belongs. 

Articulations. — With four bones — the scaphoid above, the trapezoid and second metacarpal 
bones internally, the first metacarpal below. 

Attachment of Muscles. — Abductor pollicis, Opponens pollicis, and sometimes the superficial 
head of the Flexor brevis pollicis. 

The trapezoid (os multangidum minus) (Fig. 158) is the smallest bone in the 
second row. It may be known by its wedge-shaped form, the broad end of the 
wedge forming the dorsal, the narrow end the palmar, surface, and by its having 
four articular surfaces 'touching each other and separated by sharp edges. 

Palmar For 

surface trapesium 




Fig. 158. — The left trapezoid. A, as seen from above, inner side and behind; B, from in front. 



Surfaces. — The superior surface, quadrilateral in form, smooth, and slightly con- 
cave, articulates with tiie .scaphoid. The inferior surface articulates with the upper 
end of the second metacarpal bone; it is convex from side to side, concave from 
before backward, and subdivided by an elevated ridge into two unequal lateral 
facets. The posterior or dorsal and anterior or palmar surfaces are rough, for the 
attachment of ligaments, the former being the larger of the two. The external 
surface, convex and smooth, articulates with the trapezium. The internal surface 
is concave and smooth in front, for articulation with the os magnum; rough behind, 
for the attachment of an interosseous ligament. 

To ascertain to which hand this bone belongs, let the broad dorsal surface be held upward, 
and the inferior concavo-convex surface forward; the internal concave surface will then point 
to the side to which the bone belongs 

Articulations. — With four bones — the scaphoid above, second metacarpal bone below, trape- 
zium externally, os magnum internally. 

The OS magnum {os capitatum) (Fig. 159) is the largest bone of the carpus, 
and occupies the centre of the wrist. It presents, above, a rounded portion or 
head, which is recei\"ed into the conca^'ity formed by the scaphoid and semilunar 
bones; a constricted portion or neck; and, below, the body. 

Surfaces. — The superior surface is rounded, smooth, and articulates with the semi- 
lunar. The inferior surface is divided by two ridges into three facets for articu- 
lation with the second, third, and fourth metacarpal bones, that for the third (the 
middle facet) being the largest of the three. The posterior or dorsal surface is 
broad and rough; the anterior or palmar, narrow, rounded, and also rough, for the 



200 



SPECIAL ANATOMY OF THE SKELETON 



attachment of ligaments, and it gives origin to a part of the Adductor obHquus 
polHcis. The external surface articulates with the trapezoid by a small facet 
at its anterior inferior angle, behind which is a rough depression for the attach- 
ment of an interosseous ligament. Above this is a deep and rough groove, which 
forms part of the neck and serves for the attachment of ligaments, bounded supe- 
riorly by a smooth, convex surface for articulation with the scaphoid. The 



For scaphoid 



For trapezoid 




For semilunar 



For 3rd 
For %nd metacarpal 
metacarpal 




For 4th metacarpal Palmar surface 



Fig. 159. — The left os magnum. A, outer side seen from below; B, internal posterior surface. 

internal surface articulates with the unciform by a smooth, concave, oblong 
facet which occupies its posterior and superior parts, and is rough in front, for 
the attachment of an interosseous ligament. 

To ascertain to which hand this bone belongs, the rounded head should be held upward, and 
the broad dorsal surface forward; the internal concave articular surface will point to the side to 
which the bone belongs. 

Articulations. — With seven bones — the scaphoid and semilunar above; the second, third, and 
fourth metacarpal below; the trapezoid on the radial side; and the unciform on the ulnar side. 

Attachment of Muscles. — Part of the Adductor obliquus pollicis. 

The unciform {os hamahim) (Fig. 160) may be readily distinguished by its 
wedge-shaped form and the hook-like process that projects from its palmar surface. 
It is situated at the inner and lower angle of the carpus, with its base downward, 
resting on the two inner metacarpal bones, and its apex directed upward and 
outward. 



For semilunar 




For cuneifor? 



For OS magnum — 




For ith metacarpal 

For 5th metacarpal Unciform process For 5th metacarpal 

A B 

Fig. 160. — The left unciform. A, internal surface; B, outer and distal surfaces. 

Surfaces. — The superior surface, the apex of the wedge, is narrow, convex, 
smooth, and articulates with the semilunar. The inferior surface articulates with 
the fourth and fifth metacarpal bones, the concave surface for each being sepa- 
rated by a ridge which runs from before backward. The posterior or dorsal 
surface is triangular and rough, for ligamentous attachment. The anterior or 
palmar surface presents, at its lower and inner side, a curved, hook-like process of 
bone, the imciform process (hamulus ossis hamati), directed from the palmar sur- 
face forward and outward. It gives attachment by its apex to the annular liga- 



THE METACARPUS 201 

ment and insertion to some of the fibres of the Flexor carpi uhiaris; by its inner 
surface it gives origin to the Flexor brevis minimi digiti and the Opponens niininii 
digiti; and is grooved on its outer side, for the passage of the Flexor tendons into 
the palm of the hand. This is one of the four eminences on the front of the carpus 
to which the anterior annular ligament is attached, the others being the pisiform 
internally, the oblique ridge of the trapezium and the tuberosity of the scaphoid 
externally. The internal surface articulates with the cuneiform by an oblong 
facet cut obliquely from above, downward and inward. The external surface 
articulates with the os magnum by its upper and posterior part, the remaining 
portion being rough, for the attachment of ligaments. 

To ascertain to which hand it belongs, hold the apex of the bone upward, and the broad dorsal 
surface backward; the concavity of the process will be on the side to which the bone belongs. 

Articulations. — With five bones — the semilunar above, the fourth and fifth metacarpal 
below, the cuneiform internally, the os magnum externally. 

Attachment of Muscles. —To three — the Flexor brevis minimi digiti, the Opponens 
minimi digiti, the Flexor cari)! ulnaris. 



The Metacarpus (Ossa Metacarpalia) (Figs. 150, 151). 

The metacarpal bones are five in number, and they.are numbered from 1 to 5 
inclusive, the first being the metacarpal bone of the thumb, the fifth the meta- 
carpal bone of the little finger. They are long, cylindrical bones, presenting for 
examination a shaft and two extremities. 

Common Characters of the Metacarpal Bones. — The shaft (corpus) is pris- 
moid in form, and curved longitudinally, so as to be convex in the longitudinal 
direction behind, concave in front. It presents three surfaces — two lateral and 
one posterior. The two lateral surfaces constitute the palmar or volar aspect. 
The lateral surfaces are concave, for the origin of the Interossei inuscles, and 
separated from one another by a prominent anterior ridge. The posterior or 
dorsal surface presents in its distal half a smooth, triangular, flattened area which 
is covered, in the recent state, by the tendons of the Extensor muscles. This 
triangular surface is bounded by two lines, which commence in small tubercles 
situated on the dorsal aspect on either side of the digital extremity, and, running 
backward, converge to meet some distance behind the centre of the bone and 
form a ridge which runs along the rest of the dorsal surface to the carpal ex- 
tremity. This ridge separates two lateral, sloping surfaces for the origin of the 
Dorsal interossei muscles.' To the tubercles on the digital extremities are 
attached the lateral ligaments of the metacarpophalangeal joints. On the pal- 
mar surface of each metacarpal bone is a nutrient foramen, which opens into a 
nutrient canal. In the first metacarpal the direction of this foramen is toward the 
phalanges (distad). In each of the other metacarpals it is from the phalanges 
(proximad). 

The carpal or proximal extremity (bask) is of a cuboidal form, and broader 
behind than in front; it articulates above with the carpus, and on each side 
with the adjoining metacarpal bones; its dorsal and palmar surfaces are rough, 
for the attachment of tendons and ligaments. 

The distal extremity (capltulum) presents an oblong surface, markedly con- 
vex from before backward, less so from side to side, and flattened laterally; it 
articulates with the proximal phalanx; it is broader and extends farther forward 
on the palmar than on the dorsal aspect. It is longer in the antero-posterior than 
in the transverse diameter. On either side of the head is a tubercle for the attach- 

the hand mav be at once differentiated from the metatarsal 



202 



SPECIAL ANATOMY OF THE SKELETON 



ment of the lateral ligament of the metacarpophalangeal joint. The posterior 
surface, broad and flat, supports the Extensor tendons; the anterior surface is 
grooved in the middle line for the passage of the Flexor tendons, and marked on 
each side by an articular eminence continuous with the terminal articular surface. 
The metacarpal spaces (spatia interossea metacarpi) 
are the intervals between the metacarpal bones. 
They are occupied by the Interossei muscles. The 
broadest space is between the metacarpal bones of 
the thumb and index finger. 

Peculiar Characters of the Metacarpal Bones. 
— The metacarpal bone of the thumb (o« metacar- 
pale I) (Fig. 161) is shorter and wider than the 
rest, diverges to a greater degree from the carpus, 
and its palmar surface is directed inward toward 
the palm. The shaft is flattened and broad on 
its dorsal aspect, and does not present the ridge 
which is found on the other metacarpal bones; it 
is concave from above downward, on its palmar 
surface. The carpal extremity, or base, presents 
a concavo-convex surface, for articulation with the 
trapezium; it has no lateral facets, but presents 
externally a tubercle for the insertion of the Extensor ossis metacarpi poUicis. 
The distal extremity is less convex than that of the other metacarpal bones, broader 
from side to side than from before backward. It presents on its palmar aspect 
two distinct articular eminences for the two sesamoid bones in the tendons of 
the Flexor brevis pollicis, the outer one being the larger of the two. 




Tubercle 
Foi ti ape'sium. For trape: 

Fig. 161.— The first metacarpal. (Left.) 



The side to which this bone belongs may be known by holding it in the position it occupies 
in the hand, with the carpal extremity upward and the dorsal surface backward; the tubercle for 
the Extensor ossis metacarpi pollicis will point to the side to which it belongs. 

Attachment of Muscles. — To four — the Opponens pollicis, the Extensor ossis metacarpi 
pollicis, the Flexor brevis pollicis, and the First dorsal interosseous. 

The metacarpal bone of the index finger (os metacarpaJe II) (Fig. 162) is the 
longest and its base the largest of the other fcfir. Its carpal extremity is prolonged 
upward and inward, forming a prominent ridge. The dorsal and palmar surfaces 
of this extremity are rough, for the attachment of tendons and ligaments. It pre- 
sents four articular facets — three on the upper aspect of the base; the middle 
one of the three is the largest, concave from side to side, convex from before back- 
ward, for articulation with the trapezoid; the external one is a small, flat, oval 
facet, for articulation with the trapezium; the internal one on the summit of the 
ridge is long and narrow, for articulation with the os magnum. The fourth facet 
is on the inner or the ulnar side of the extremity of the bone, and is for articulation 
with the third metacarpal bone. 

The side to which this bone belongs is indicated by the absence of the lateral facet on the outer 
(radial) side of its base, so that if the bone is placed with the base toward the student and the 
palmar surface upward, the side on which there is no lateral facet will be that to which it belongs. 

Attachment of Muscles. — To six — Flexor carpi radialis, Extensor carpi radiahs longior, 
the deep portion of the Flexor brevis pollicis. First and Second dorsal interosseous, and First 
palmar interosseous. 



The metacarpal bone of the middle finger (os metacarpale III) (Fig. 163) is a 
little smaller than the preceding; it presents a pyramidal eminence, the styloid 



THE METACARPUS 



203 



process {processus styloideus), on the radial side of its base (dorsal aspect), wliicl) 
extends upward behind the os magnum; immediately below this, on the dorsal 
aspect, is a rough surface for the attachment of the Extensor carpi radialis brevior. 
The carpal, articular facet is concave behind, flat in front, and articulates with the 
OS magnum. On the radial side is a smooth, concave facet, for articulation with 
the second metacarpal bone, and on the ulnar side two small, oval facets, for articu- 
lation with the fourth metacarpal. 

_ The side to which this bone belongs is easily recognized by the styloid process on the radial 
side of its base. With the palmar surface uppermost and the base toward the student, this process 
points toward the side to which the bone belongs. 

Attachment of Muscles.— To s?.r~E\-tensor carpi radialis brevior. Flexor carpi radialis. 
Adductor transversus pollicis, Adductor obliquus pollicis, and Second and Thu-d dorsal inter- 
osseous. 





. For third metacarpal 
Sor trapezoid. For os magiiuvi. 

Fig. 162. — The second metacirp.il. (Left.) 




For fourlh 
metacarpal. 



SlyloiH For second 
process, metacarpal. 

For OS magnum. 

Fig. 163.— The third metacarpal. (Left.) 



The metacarpal bone of the ring finger (os metacarpale IV) (Fig. 164) is shorter 
and smaller than the preceding, and its base small and quadrilateral; the carpal 
surface of the base presenting two facets, a large one internally, for articulation 
with the unciform, and a small one externally, for the os magnum. On the 
radial side are two oval facets, for articulation with the third metacarpal bone; 
and on the ulnar side a single concave facet, for the fifth metacarpal. 

If this bone is placed with the base toward the student and the palmar surface upward, the 
radial side of the base, which has two facets for articulation with the third metacarpal bone, wili 
be on the side to which it belongs. If, as sometimes happens in badly marked bones, one of these 
facets is indistinguishable, the side may be known by selecting the surface on which the larger 
articular facet is present. This facet is for the fifth metacarpal bone, and would therefore be 
situated on the ulnar side— that is, the one to which the bone does not belong. 

Attachment of Muscles.— To three— the Third and Fourth dorsal and Second palmar inter- 



The metacarpal bone of the little finger (os meiacarfaJe V) (Fig. 165) presents 
on its base one facet, which is concavo-convex, and which articulates with the 
unciform bone, and one lateral, articular facet, which articulates with the fourth 
metacarpal bone. On its ulnar side is a prominent tubercle, for the insertion of 



204 



SPECIAL ANATOMY OF THE SKELETON 



the tendon of the Extensor carpi ulnaris. The dorsal surface of the shaft is marived 
by an obhque ridge which extends from near the ulnar side of the upper extremity 
to the radial side of the lower. The outer division of this surface serves for 
the attachment of the Fourth dorsal interosseous muscle; the inner division is 
smooth and covered by the Extensor tendons of the little finger. 



L-'^N 



For third 
metacarpal. For os 
magnum. 



For fift h meta- 
carpal 
For unciform. 



Fig. 164.— The fourth metacarpal. (Left.) 



For unciform, 
metacarpal. 

Fig. 16S.— The fifth metacarpal. (Left.) 



If thi.s Vione is placed with its base toward the student and its pahnar surface upward, the 
side of the head wiiich has a lateral facet will be that to which the bone belongs. 

Attachment of Muscles. — To five — the E.xtensor carpi ulnaris, Fle.xor carpi ulnaris, Oppo- 
nens minimi digiti. Fourth dorsal, and Third palmar interossei. 

Articulations. — Besides the phalangeal articulations, the first metacarpal bone articulates 
with the trapezium; the second with the trapezium, trapezoid, os magnum, and third metacarpal 
bones; the third with the os magnum and second and fourth metacarpal bones; the fourth with, 
the OS magnum, unciform, and third and fifth metacarpal bones; and the fifth with the unciform 
and fourth metacarpal. 

Th.^ first has no lateral facets on its carpal extremity; the second has no lateral facet on its 
radial side, but one on its ulnar side; the third has one on its radial and two on its ulnar side; 
the fourth has two on its radial and one on its. ulnar side; and the fifth has only one on its radial 
side. 



The Phalanges of the Hand (Phalanges Digitorum Manus). 

The phalanges (phalanges digitorum manus) are fourteen in number, three for 
each finger, and two for the thumb. In numbering them the proximal bone 
is designated as the first phalanx (phalan.v I). They are long bones, and present 
for examination a shaft and two extremities. The shaft (corpus phaJangis) 
tapers from above downward, is convex posteriorly, concave in front from above 
downward, flat from side to side, and marked laterally by rough ridges, which 
give attachment to the fibrous sheaths of the Flexor tendons. A nutrient foramen 
on the palmar surface leads into a nutrient canal which runs toward the periphery 
(distad). The metacarpal extremity, or base (basis plialangis), of each phalanx 
in the first row presents an oval, concave, articular surface, broader from side 
to side than from before backward; and the same extremity in the other two 
rows, a double concavity, separated by a longitudinal median ridge, extending 
from before backward. The distal extremity of the first phalanx of the thumb 



THE PHALANGES OF THE HAND 205 

and of the first and second phalanx of each of the fingers is smaller than the 
base, and terminates in two small, lateral condyles, separated by a slight groove 
(trochlea phahnqis); the articnlar surface being prolonged farther forward on 
the palmar than on the dorsal surface, especially in the first row. 

The ungual phalanges (distal) are convex on their dorsal, flat on their palmar, 
surfaces; they are recognized by their small size and by a roughened, elevated 
surface of a horseshoe form on the palmar aspect of their ungual extremity (tuber- 
ositas luujuicularis), which serves to support the sensitive pulp of the finger. 

Articulations. — The first row, with the metacarpal bones and the second row of phalanges; 
the second row, with the first and third; the third, with the second ro^\'. 

Attachment of Muscles.— To the base of the first phalanx of the thumb, ^w muscles— the 
Extensor brevis [joUicis, Flexor brevis poliicis. Abductor pollicis, Adductores transversus and 
Obliquus pollicis. To the second phalanx, two — the Flexor longus pollicis and the Extensor 
Jongus pollicis. To the base of the first phalanx of the index finger, the First dorsal and the First 
palmar interosseous; to that of the middle finger, the Second and Third dorsal interosseous; 
to that of the ring finger, the Fourth dorsal and the Second palmar interossei; and to 
that of the little finger, the Third palmar interosseous, the Flexor brevis minimi digiti, and 
Abductor minimi digiti. To the second phalanges, the Flexor sublimis digitorum. Extensor 
communis digitorum, and, in addition, the Extensor indicis to the index finger, the Extensor 
minimi digiti to the little finger. To the third phalanges, the Flexor profundus digitorum and 
Extensor communis digitorum. 

Surface Form of Carpal and Metacarpal Bones and of the Phalanges.— On the 
front of tlie wrist are two subcutaneous eminences, one on the radial side, the larger and 
flatter, due to the tuberosity of the scaphoid and tlie ridge on the trapezium; the other, on 
the ulnar side, caused by the pisiform bone. The tubercle of the scaphoid may be felt just 
below and in front of the apex of the styloid process of the radius. It is best perceived by 
■extending the hand on the forearm. Immediately below may be felt another prominence, better 
marked than the tubercle; this is the ridge on the trapezium which gives attachment to some of 
the short muscles of the thumb. On the inner side of the front of the wrist the pisiform bone 
may be felt, forming a small but prominent projection in this situation. It is some distance below 
the styloid process of the ulna, and may be said to be just below the level of the styloid process of 
the radius. The rest of the front of the carpus is covered by tendons and the annular ligament, 
and entirely concealed, with the exception of the hooked process of the unciform, which can only 
be made out with difficulty. The back of the carpus is convex and covered by the Extensor ten- 
dons, so that none of the posterior surfaces of the bones are to be felt, with the exception of the 
cuneiform on the inner side. Below the carpus the dorsal surfaces of the metacarpal bones, 
except the fifth, are covered by tendons, and are scarcely visible e.xcept in very thin hands. The 
dorsal surface of the fifth is, however, subcutaneous throughout almost its whole length, and may 
be plainly perceived and felt. In addition to this, slightly external to the middle line of the hand, 
is a prominence, frequently well marked, but occasionally indistinct, formed by the base of the 
metacarpal of the middle finger. The heads of the metacarpal bones may be plainly felt and seen, 
rounded in contour and standing out in bold relief under the skin, when the fist is clenched. It 
should be borne in mind that when the fingers are flexed on the hand, the articular surfaces of 
the first phalanges glide off the heads of the metacarpal bones on to their anterior surfaces, so 
that the head of these bones form the prominence of the knuckles and receive the force of any 
blow which may be given. The head of the third metacarpal bone is the most prominent, and 
receives the greater part of the shock of the blow. This bone articulates with the os magnum, 
so that the concussion is carried through this bone to the scaphoid and semilunar, with which the 
head of the os magnum articulates, and by these bones is transferred to the radius, along which 
it may be carried to the capitellum of the humerus. The enlarged extremities of the phalanges 
may be plainly felt; they form the joints of the fingers. When the digits are bent the proximal 
phalanges of the joints form prominences, which in the joint between the first and second pha- 
langes is slightly hollowed, in accordance with the grooved shape of their articular surfaces, 
while at the last row the prominence is flattened and square-shaped. In the palm of the hand 
the four inner metacarpal bones are covered by muscles, tendons, and the palmar fascia, and no 
part of them but their heads is to be distinguished. With regard to the thumb, on the dorsal 
aspect the base of the metacarpal bone forms a prominence below the styloid process of the radius; 
the shaft is to be felt, covered by tendons, terminating at its head in a flattened pi'ominence, in 
front of which can be felt the sesamoid bones. 

Applied Anatomy. — The carpal bones are not very liable to fracture, except from extreme 
violence, when the parts may be so comminuted as to necessitate amputation. Occasionally 
they are the seat of tubemdous disease. The metacarpal bones and the phalanges are not infre- 
quently broken by direct violence. The first metacarpal bone is the one most commonly frae- 



206 



SPECIAL ANATOMY OF THE SKELETON 



tured; then the second, the fourth, and the fifth, the third being the one least frequently broken. 
There are two diseases of the metacarpal bones and phalanges which require special mention on 
account of the frequency of their occurrence. One is tuberculous dactylitis, consisting in a deoosit 
of tuberculous material in the medullary canal, expanding the bone, with subsequent caseadon 
and resulting necrosis. The other is chondroma, which is perhaps more frequently found in 
connection with the metacarpal bones and phalanges than with any other bones. When chon- 
dromatous growth takes place there are usually multiple tumors, and they may spring either 
from the medullary canal or from the periosteum. • ■ 

Development of the Bones of the Hand. — The carpal bones are each developed from a 
single centre. At birth they are all cartilaginous. Ossification proceeds in the following order 
(Fig. 166): In the os magnum and unciform an ossific point appears during the first year, the 
former preceding the latter; in the cuneiform, at the third year; in the trapezium and semilunar, 
at the -fifth year, the latter preceding the former; in the scaphoid, in the si.\th to the eighth year; 
in the trapezoid, during the eighth year; and in the pisiform, about the twelfth year. 



Appears 3rd year. 

Unite Wth year. 
Appears 8th week. 




Carpus. 

One centre for each bone 
Alt cartilaginous at butti. 



Metacarpus. 

Two centres for each tone • 
One for shaft, 
One for distal extremity, 
except first. 



Phalanges. 

Two centres for eacli bone [IJ 
One for shaft, 
One for metacarpal 
extremity. 



^Appears ttih-Sth year. 
Unite IStli-SOth year. 
§, ^l^i—Apnears 8th week. 

Appears Uh-Sth year. 
Unite ISth-SO year. 
.^ I [-^Appears 8th week. 

Fig. 166. — Plan of the development of the bones of the hand. 

Occasionally an additional bone, the os centrale, is found in the carpus, lying between the 
scaphoid, trapezoid, and oS magnum. During the second month of fetal life it is represented 
by a small cartilaginous nodule, which, however, fuses with the cartilaginous scaphoid about the 
third month. Sometimes the styloid process of the third metacarpal is detached and forms an 
additional os.sicle. 

The metacarpal bones are each developed from ttvo centres, one for the shaft and one for 
the distal extremity for the four inner metacarpal bones; one for the shaft and one for the base 
for the metacarpal bone of the thumb, which in this respect resembles the phalanges.' Ossi- 
fication commences in the centre of the shaft about the eighth or ninth week, the centre for the 
first metacarpal bone being the last to appear; ossification gradually proceeds to either end of 

' Allan Thomson has demonstrated the fact that the first metacarpal bone is often developed from three centres; 
that is to say, there is separate nucleus for the distal end, forming a distinct epiphysis, visible at the age of seven or 
eight years. He also states that there are traces of a proximal epiphysis in the second metacarpal bone. — Journal of . 
Anatomy and Physiology, 1S69. 



THE OS INNOMINA TUM 207 

the bone: about the third year the distal extremities of the four inner nietaoarpal bones and the 
base of the first metacarpal begin to ossify, and they unite with the shaft about the twentieth year. 

The phalanges are each developed from two centres, one for the shaft and one for the base. 
Ossification commences in the shaft, in all three rows, at about the eighth week, and gradually 
involves the whole bone excepting the upper extremity. Ossification of the base commences in 
the first row between the third and fourth years, and a year later in those of the second and third 
rows. The two centres become united, in each row, between the eighteentli and twentieth years. 

In the ungual phalanges the centre for the shaft appears at the distal extremity of the phalanx, 
instead of at the middle of the shaft, as is the case with the other phalanges. The ungual 
phalanges are the first boiies of the hands to begin to ossify. 



THE LOWER EXTREMITY. 

The lower extremity consists of the following bones: Ossa innominata (with 
the sacrum and coccyx forming the pelvis), the femur (thigh), the tibia and 
fibula (the leg), the tarsus, the metatarsus and phalanges {(ht foot). 



THE OS INNOMINATUM, CALLED ALSO OS COXAE, HIP BONE (Figs. 167, 168). 

The OS iimonunatlun is a large, irregularly shaped, flat bone, constricted in the 
centre and expanded above and below. With its fellow of the opposite side it 
forms the sides and anterior wall of the pelvic cavity. In young subjects it 
consists of three separate parts, which meet and form the large, cup-like cavity, 
the acetabulum, situated near the middle of the outer surface of the bone; and, 
although in the adult these have become united, it is usual to describe the bone 
as divisible into three portions — the ilium, the ischium, and the pubis. 

The ilium is the superior, broad, and expanded portion which runs upward 
from the acetabulum and forms the prominence of the hip. 

The ischium is the inferior and strongest portion of the bone ; it proceeds down- 
ward from the acetabulum, expands into a large tuberosity, and then, curving 
forward, helps to bound, with the descending ramus of the os pubis, a large 
aperture, the obturator foramen. 

The OS pubis is that portion which extends inward and downward from the 
acetabulum to articulate in the middle line with the bone of the opposite side; it 
forms the front of the pelvis and supports the external organs of generation. 

The Ilium (os ilium) presents for examination two surfaces, an external and 
an internal, a crest, and two borders, an anterior and a posterior. 

The external surface (Fig. 167) is divided into two parts — an upper or gluteal 
and a lower or acetabular. The upper portion — known as the dorsum ilii — is 
directed backward and outward behind, and downward and outward in front. 
It is smooth, convex in front, deeply concave behind; bounded above by the crest, 
beloio by the upper border of the acetabulum; in front and behind by the anterior 
and posterior borders. This surface is crossed in an arched direction by three 
semicircular lines — the superior, middle, and inferior curved lines. The superior 
curved line (linea glutaea posterior), the shortest of the three, commences at the 
crest, about two inches in front of its posterior extremity; it is at ftrst distinctly 
marked, but as it passes downward and backward to the upper part of the great 
sacrosciatic notch, where it terminates, it becomes less marked, and is often alto- 
gether lost. Behind this line is a narrow semilunar surface, the upper part of 
vyhich is rough and affords origin to part of the Gluteus maximus; the lower part 
is smooth and has no muscle fibres attached to it. The middle curved line (linea 
glutaea anterior), the longest of the three, commences at the crest, about an inch 
behind its anterior extremity, and, taking a curved direction downward and 
backward, terminates at the upper part of the great sacrosciatic notch. The 



208 



SPECIAL ANATOMY OF THE SKELETON 



space Ijetween the superior and middle curved lines and the crest is concave, 
and affords origin to the Gluteus medius muscle. Near the central part of this 
line may often be observed the orifice of a nutrient foramen. The inferior curved 



Anterior superior 




CTOR LONGUS 



GEMELLUS INFERIOR 



Fig. 167. — Right os innominatum. E.xternal surface. 

line {linea glutaea inferior), the least distinct of the three, commences in front 
at the notch on the anterior border, and, taking a cun'ed direction backward 
and downward, terminates at the middle of the great sacrosciatic notch. The 
surface of bone included between the middle and inferior curved lines is concave 
from above downward, convex from before backward, and affords origin to the 
Gluteus minimus muscle. Beneath the inferior curved line, and corresponding 
to the upper part of the acetabulum, is a roughened surface (sometimes a depres- 
sion), from which arises the reflected tendon of the Rectus femoris muscle. 
The lower or acetabular part of the external surface enters into the formation 



THE OS INNOMINATUM 



209 



of the acetabulum, of which it forms rather less than two-fifths. It is separated 
from tlie gluteal portion by a prominent rim, which forms part of the margin 
of the acetabular cavity. 




COMPRESSOR L 

Cnts penis/ erector penje 

Fig. 168. — Right os innominatum. Internal surface. 

The internal surface (Fig. 168) is bounded above by the crest; belotv it is con- 
tinuous with the pelvic surface of the os pubis and ischium, a faint line only 
indicating the place of union; and before and behind it is bounded by the 
anterior and posterior borders. It presents a large, smooth, concave surface, 
called the iliac fossa (fossa iliaca), which lodges the Iliacus muscle, and presents 
at its lower part the orifice of a nutrient canal, and below this a smooth, rounded 
border, the iliopectineal line (linea arcuata). which separates the iliac fossa from that 
portion of the internal surface which enters into the formation of the true pelvis, 
and which gives origin to part of the Obturator internus muscle. Behind the 
iliac fossa is a rough surface divided into two portions, an anterior and a posterior 

14 



210 SPECIAL ANATOMY OF THE SKELETON 

The anterior or auricular portion { fades aiiricidaris) , so called from its resemblance 
in shape to the ear, is coated with cartilage in the recent state, and articulates 
with a surface of similar shape on the side of the sacrum. The posterior portion 
(ivherositas iliaca) is rough, for the attachment of the posterior sacroiliac ligaments 
an,d for a part of the origin of the Erector and Multifidus spinae. 

The crest of the ilium (crista iliaca) is convex in its general outline and sinuously 
curved, being concave inward in front, concave outward behind. It is longer in 
the female than in the male, very thick behind, and thinner at the centre than at 
the extremities. It terminates at either end in a prominent eminence, the anterior 
superior and posterior superior spinous process {spina iliaca anterior superior el 
spina iliaca posterior superior). The surface of the crest is broad, and divided 
into an external lip (labium externmn), an internal lip (labium internum), and- an 
intermediate space (linea intermedia). About two inches behind the anterior 
superior spinous process there is a prominent tubercle on the outer lip. To the 
external lip is attached the Tensor fasciae femoris, Obliquus externus abdominis, 
and Latissimus dorsi, and along its whole length, the fascia lata; to the space 
between the lips, the Internal oblique; to the internal lip, the Transversalis, 
Quadratus lumborum, and Erector spinae, the Iliacus, and the iliac fascia. 

The anterior border of the ilium is concave. It presents two projections, sepa- 
rated by a notch. Of these, the uppermost, situated at the junction of the crest 
and anterior border, is called the anterior superior spinous process of the ilium, 
the outer border of which gives attachment to the fascia lata and the origin of 
the Tensor fasciae femoris; its inner border, to the Iliacus; while its extremity 
affords attachment to Poupart's ligament and the origin of the Sartorius. Beneatli 
this eminence is a notch which gives origin to the Sartorius muscle, and across 
which passes the external cutaneous nerve. Below the notch is the anterior 
inferior spinous process (spina iliaca anterior inferior), which terminates in the 
upper lip of the acetabulum; it gives origin to the straight tendon of the Rectus 
femoris muscle and the iliofemoral ligament. On the inner side of the anterior 
inferior spinous process is a broad, shallow groove, over which passes the Ilio- 
psoas muscle. This groove is bounded internally by an eminence, the iliopectineal 
eminence (eminentia iliopectinea) , which marks the point of union of the ilium and 
OS pubis. 

The posterior border of the ilium, shorter than the anterior, also presents two 
projections separated by a notch, the posterior superior spinous process (spi7ia 
iliaca posterior superior) and the posterior inferior spinous process (spina iliaca 
posterior inferior). The former corresponds \\ith that portion of the inner 
surface of the ilium which serves for the attachment of the oblique portion of the 
sacroiliac ligaments and the Multifidus spinae muscle; the latter, to the auricular 
portion which articulates with the sacrum. Below the posterior inferior spinous, 
process the posterior border forms the upper part of a deep notch, the great 
sacrosciatic notch. 

The Ischium (os ischii) forms the lower and back part of the os innominatum. 
It is di^'isible into a thick and solid portion — the body; a large, rough eminence, 
on W'hich the trunk rests in sitting — the tuberosity; and a thin part which passes 
inward and slightly upward — the ramus. 

The body (corpus ossis ischii), somewhat triangular in form, presents three 
surfaces, antero-external, internal, and postero-external ; and three borders, ex- 
ternal, internal, and posterior. The antero-external surface corresponds to that 
portion of the acetabulum formed by the ischium; it is smooth and concave, 
and forms a little more than two-fifths of the acetabular cavity; its outer margin 
is bounded by a prominent rim or lip, the external border, to which the cotyloid 
fibrocartilage is attached. Below the acetabulum, between it and the tuberosity, 
is a deep groove, along w-hich the tendon of the Obturator externus muscle runs 



THE OH INNOMINATUM 211 

as it passes outward to be inserted into the trochanteric fossa of the femur. 
The internal surface is smooth, concave, and enters into the formation of the lateral 
boundary- of the true peh'ic canity. This surface is perforated by two or three 
large, vascular foramina, and affords origin to part of the Obturator internus 
muscle. The postero-external surface is quadrilateral in form, broad and smooth. 
Below, where it joins the tuberosity, it presents a groove, the obturator groove 
(sulcus ohturatorius) , continuous with that on the antero-external surface; in 
this groo\'e is received the posterior fleshy part of the Obturator externus muscle 
when the thigh is flexed. The lower edge of this groove is formed by the tuberosity 
of the ischium, and affords origin to the Gemellus inferior muscle. The postero- 
external surface is limited, externally, by the margin of the acetabulum; behind, 
by the posterior border; it supports the Pyriformis, the two Gemelli, and the 
Obturator internus muscles in their passage to the great trochanter. The ex- 
ternal border separates the postero-external from the antero-external surface. 
The internal border is thin, and forms the outer circumference of the obturator 
foramen. The posterior border of the body of the ischium is continuous with 
the posterior border of the ilium; it presents, a little below the centre, a thin 
and pointed triangular eminence, the spine of the ischium {spina ischiadica), 
more or less elongated in different subjects; its external surface gives origin 
to the Gemellus superior, its internal surface to the Coccygeus and Levator 
ani; while to the pointed extremity is connected the lesser .sacrosciatic ligament. 
Above the spine is a notch of large size, the great sacrosciatic notch, converted into 
a foramen, the great sacrosciatic foramen (foramen ischiadicum majus), by the 
lesser and greater sacrosciatic ligaments; it transmits the Pyriformis muscle, 
the gluteal vessels, and superior and inferior gluteal nerves; the sciatic vessels, 
the greater and lesser sciatic nerves, the internal pudic vessels and nerve, and the 
nerves to the Obturator internus and Quadratus femoris. Of these, the gluteal 
vessels and superior gluteal nerve pass out above the Pyriformis muscle, the other 
structures, below it. Below the spine is a smaller notch, the lesser sacrosciatic 
notch (incisura ischiadica minor); it is smooth, coated in the recent state with 
cartilage. It is converted into a foramen, the lesser sacrosciatic foramen (foramen 
ischiadicum minus), by the sacrosciatic ligaments, and transmits the tendon of 
the Obturator internus, the nerve which supplies that muscle, and the internal 
pudic vessels and nerve. 

The tuberosity of the ischium (tuber ischiadicum) is the portion of bone between 
the body and the ramus. The tuberosity presents for examination three sur- 
faces — external, internal, and posterior. The external surface is quadrilateral 
in shape and rough, for the attachment of muscles. It is bounded above by 
the groove for the tendon of the Obturator externus; in front it is limited by 
the posterior margin of the obturator foramen, and below it is continuous with the 
ramus of the bone; behind, it is bounded by a prominent margin which separates 
it from tlie posterior surface. In front of this margin the surface gives origin 
to the Quadratus femoris, and anterior to this some of the fibres of origin of the 
Obturator externus. The lower part of the surface gives origin to part of the 
Adductor magnus. The internal surface forms part of the bony wall of the true 
^ pelvis. In front it is limited by the posterior margin of the obturator foramen; 
behind, it is bounded by a sharp ridge, for the attachment of a falciform pro- 
longation of the great sacrosciatic ligament; it sometimes presents a groove on 
the inner side of this ridge for the lodgement of the internal pudic vessels and nerve ; 
and, more anteriorly, has attached the Transversus perinaei and Erector penis vel 
clitoridis muscles. The posterior surface is divided into two portions — a lower 
rough, somewhat triangular part, and an upper smooth, quadrilateral portion. 
The lower portion is subdivided by a prominent y-ertical ridge, passing from 
base to apex, into two parts; the outer one gives origin to the Adductor magnus; 



212 SPECIAL ANAT03fY OF THE SKELETON 

the inner, to the great sacrosciatic hgament. The upper portion is subdivided 
into two facets by an obUque ridge which runs downward and outward ; from the 
upper and outer facet arises the Semimembranosus; from the lower and inner, 
the Biceps and Semitendinosus. 

The ramus {raimis inferior ossis ischii) is the thin, flattened part of the ischium 
which ascends from the tuberosity upward and inward, and joins the descending 
ramus of the os pubis, their point of junction being indicated in the adult by a 
rough line. The outer surface of the ramus is rough, for the origin of the Obtura- 
tor externus muscle, and also some fibres of the Adductor magnus; its inner sur- 
face forms part of the anterior wall of the pelvis. Its inner border is thick, rough, 
slightly everted, forms part of the outlet of the pelvis, and presents two ridges and 
an intervening space. The ridges are continuous with similar ones on the de- 
scending ramus of the os pubis; to the outer one is attached the deep layer of 
the superficial perineal fascia, and to the inner, the superficial layer of the tri- 
angular ligament of the perineum. If these two ridges are traced backward, 
they will be found to join with each other just behind the point of origin of the 
Transversus perinei muscle; here the two layers of fascia are continuous behind 
the posterior border of the muscle. To the intervening space, just in front of the 
point of junction of the ridges, is attached the Transversus perinei muscle, and in 
front of this arises a portion of the crus penis vel clitoridis and the Erector penis 
vel clitoridis muscle. Its outer border is thin and sharp, and forms part of the 
inner margin of the obturator foramen. 

The Pubis (os pubis) forms the anterior part of the os innominatum, and, with the 
bone of the opposite side, forms the front boundary of the true pelvic cavity. It is 
divisible into a body, a superior or ascending and an inferior or descending ramus. 

The body (corpus ossis pubis) is the broad portion of bone formed at the junc- 
tion of the two rami. It is somewhat quadrilateral in shape, and presents for ex- 
amination two surfaces and three borders. The anterior surface is rough, directed 
downward and outward, and serves for the attachment of various muscles. From 
the upper and inner angle, immediately below the upper border, arises the Adduc- 
tor longus; lower down, from without inward, arise the Obturator externus, the 
Adductor brevis, and the upper part of the Gracilis. The posterior surface, 
convex from above downward, concave from side to side, is smooth, and forms 
part of the anterior wall of the pelvis. It gives origin to the Levator ani, Obturator 
internus, a few muscle fibres prolonged from the bladder, and the puboprostatic 
ligaments. At the outer part of the upper border is a prominent tubercle, which 
projects forward and is -called the spine (tuberciduvi ptibicimi); to it is attached 
Poupart's ligament. Passing upward and outward from this is a prominent 
ridge, forming part of the iliopectineal line (linea arcuata). It marks the brim of 
the true pelvis; to it are attached a portion of the conjoined tendon of the Internal 
oblique and Transversalis muscles, Gimbernat's ligament, and the triangular 
fascia. Internal to the spine the upper border is called the crest, which ex- 
tends from this process to the inner extremity of the bone. It affords attach- 
ment to the conjoined tendon of the Internal Oblique and Trans^"e^salis, and 
to the Rectus abdominis and Pyramidalis muscles. The point of junction of 
the crest with the inner border of the bone is called the angle ; to it, as well as to 
the symphysis, is attached the internal pillar of the external abdominal ring. 
The internal border is articular; it is oval, covered by eight or nine transverse 
ridges, which serve for the attachment of a thin layer of cartilage. This surface 
is united to its fellow of the opposite side in the whole pelvis. The joint is called 
the symphysis pubis. The outer border presents a sharp margin, which forms 
part of the circumference of the obturator foramen and afi'ords attachment to 
the obturator membrane. 

The ascending ramus (ramus superior ossis pubis) extends from the body to 



THE OS INNOMINATUM 213 

the point of junction of the os pubis with the ihum, and forms the upper part 
of the circumference of the obturator foramen. It presents for examination 
a superior, inferior, and posterior surface, and an outer extremity. The supe- 
rior surface presents a continuation of the iliopectineal Hne, already mentioned as 
commencing at the pubic spine. In front of this ridge the surface of bone is 
triangular in form, wider externally than internally, smooth, and is covered by 
the Pectineus muscle. The surface is bounded externally by a rough eminence, 
the iliopectineal eminence {eminentia iliopectinea), which serves to indicate the 
point of junction of the ilium and os pubis, and gives attachment to the Psoas 
parvus, when this muscle is present. The triangular surface is bounded ijelow 
by a prominent ridge, the obturator crest (crista obturatoria), which extends from 
the cotyloid notch to the spine of the os pubis. The inferior surface forms the 
upper boundary of the obturator foramen, and presents externally a l)road and 
deep oblique groove, the obturator groove (sulcus obturaforius), for the passage 
of the obturator vessels and nerve; and internally a sharp margin which forms 
part of the circumference of the obturator foramen, and to which the obturator 
membrane is attached. The posterior surface forms part of the anterior boundary 
of the true pelvis. It is smooth, convex from above downward, and affords 
origin to some fibres of the Obturator internus. The outer extremity, the thickest 
part of the ramus, forms one-hfth of the cavity of the aceta!)ulum. 

The descending ramus (ramus inferior ossis pubis) is thin and flattened. It 
passes outward and downward, becoming narrower as it descends, and joins 
with the ramus of the ischium. Its anterior surface is rough, for the origin of 
muscles — the Gracilis along its inner border; a portion of the Obturator externus 
where the ramus enters into the formation of the obturator foramen; and be- 
tween these two muscles the Adductores brevis and magnus from within out- 
ward. The posterior surface is smooth, and gives origin to the Obturator internus, 
and, close to the inner margin, to the Compressor urethrae. The inner border is 
thick, rough, and everted, especially in females. It presents two ridges, separated 
by an intervening space. The ridges extend downward, and are continuous 
with similar ridges on the ascending ramus of the ischium; to the external one 
is attached the deep layer of the superficial perineal fascia, and to the internal 
one the superficial layer of the triangular ligament of the perineum. The outer 
border is thin and sharp, forms part of the circumference of the obturator fora- 
men, and gives attachment to the obturator membrane. 

The Cotyloid Cavity, or Acetabulum, is a deep, cup-shaped, hemispherical 
depression, directed downward, outward, and forward; formed internally by the 
os pubis, above by the ilium, behind, externally, and beloic by the ischium, a little 
less than two-fifths being formed by the ilium, a little more tlian two-fifths by the 
ischium, and the remaining fifth by the pubic bone. It is bounded by a prominent 
uneven rim, which is thick and strong above, and serves for the attachment of the 
cotyloid ligament, which contracts its orifice and deepens the surface for articula- 
tion. It presents below and internally a deep notch, the cotyloid notch (incisura 
ucetabuli), which is continuous with a circular depression, the fossa of the ace- 
tabulum (fossa acetabuli), at the bottom of the cavity; this depression is perforated 
by numerous apertures, lodges a mass of fat, and its margins, as well as those of 
the notch, serve for the attachment of the ligamentum teres. The fossa acetabuli 
is partly surrounded by a concave rim of bone (fades lunata). The cotyloid notch 
is converted, in the natural state, into a foramen by a dense ligamentous band, 
the transverse ligament, which passes across it. Through this foramen the nu- 
trient vessels and nerA'cs of the joint pass. 

The Obturator, or Thyroid Foramen (foramen obturatum), is a large aperture 
situated between the ischium and os pubis. In the male it is large, of an oval 
form, its longest diameter being obliquely from before backward; in the female 



214 SPECIAL ANATOMY OF THE SKELETON 

it is smaller and more triangular. It is bounded by a thin, uneven margin, to 
which a strong membrane is attached, and presents, anteriorly, a deep groove, 
the obturator groove (sulcus obtiiratorius), which runs from the pelvis obliquely 
inward and downward. This groove is converted into a foramen by a ligamentous 
band, a specialized part of the obturator membrane, attached to two tubercles, 
one (tuberculum obturatorium posterkis) on the internal border of the ischium, just 
in front of the cotyloid notch, the other (tubercuhim obturatorium anterius) on the 
inferior margin of the posterior surface of the ascending ramus of the pubis, and 
transmits the obturator vessels and nerve. 

Structure. — This bone consists of much cancellous tissue, especially where it is thick, enclosed 
between two layers of dense, compact tissue. In the thinner parts of the bone, as at the bottom 
of the acetabulum and centre of the iliac fossa, it is usually semitransparent, and composed 
entirely of compact tissue. 

Development (Fig. 169). — From eight centres — three primary, one for the ilium, one for the 
ischium, and one for the os pubis; and five secondary, one for the crest of the ilium, one for the 
anterior inferior spinous process (said to occur more frequently in the male than in the female), 
one for the tuberosity of the ischium, one for the symphysis pubis (more frequent in the female 
than the male), and one or more for the Y-shaped piece at the bottom of the acetabulum. These 



„ ■ ,, J \ Three primary {Ilium, Ischium, and Os Pubis). 

F'-om eight centres ip^^^^^^y^^ 



S. Symphysis pub/: 




The three primary centres unite through a V-shaped piece about puberty. 
Epiphyses appear about puberty, and unite about the twenty-Jifth year. 

Fig. 169. — Plan of the development of the os innominatum. 

various centres appear in the following order: First, in the ilium, at the lower part of the bone, 
immediately above the sciatic notch, at about the eighth or ninth week; secondly, in the body of 
the ischium, at about the third month of fetal life; thirdly, in the body of the os pubis, between 
the fourth and fifth months. At birth the three primary centres are quite separate, the crest, the 
bottom of the acetabulum, the ischial tuberosity, and the rami of the ischium and pubes being 
still cartilaginous. At about the seventh or eighth year the rami of the os pubis and ischium are 
almost completely united by bone. About the twelfth year the three divisions of the bone have 
extended their growth into the bottom of the acetabulum, being separated from each other by a 
Y-shaped portion of cartilage, which now presents traces of ossification, often by two or more 
centres. One of these, the os acetahuli, appears about the age of twelve, between the ilium and os 
pubis, and fuses with them about the aeeof eighteen. It forms the pubic part of the acetabulum. 
The ilium and ischium then become joined, and lasdy the os pubis to the ischium, through the 



THE PELVIS 215 

intervention of this Y-shaped portion. At about the age of puberty ossification, takes place 
in each of the remaining portions, and they become joined to the rest of the bone between the 
twentieth and twenty-fifth years. Separate centres are frequently found for the pubic and ischiiil 
.spines. 

Articulations. — ^Yith its fellow of the opposite side, the sacrum, and femur. 

Attachment of Muscles.— To the ilium, sixteen. To the outer lip of the crest, the Tensor 
vaginae femoris, Obliquus externus abdominis, and Latissimus dorsi; to the internal lip, the 
Iliacus, Transversalis, Quadratus lumborum, and Erector spinae; to the intenspace between the 
lips, the Obliquus internus. To the outer surface of the ilium, the Gluteus maximus. Gluteus 
medius. Gluteus minimus, reflected tendon of the Rectus femoris; to the upper part of the great 
sacrosciatic notch, a portion of the Pyriformis; to the internal surface, the Iliacus; to that portion 
of the internal surface below the iliopectineal line, the Obturator internus to the internal surface 
of the posterior superior spine, and the Multifidus spinae; to the anterior border, the Sartoi'ius 
and straight tendon of the Rectus femoris. To the ischium, thirteen. To the outer surface of 
the ramus, the Obturator e.xternus and Adductor magnus; to the internal surface, the Obturator 
internus and Erector penis. To the spine, the Gemellus superior, Levator ani, and Coccygeus. 
To the tuberosity, the Biceps, Semitendinosus, Semimembranosu.s, Quadi'atus femoris. Adductor 
magnus, Gemellus inferior, Transversus perinei. Erector penis. To the pubis, sixteen: Obliquus 
externus, Obliquus internus, Transversalis, Rectus abdominis, Pyramidalis, Psoas parvus, 
Pectineus, Adductor magnus, Adductor longus. Adductor brevis. Gracilis, Obturator externus 
and internus. Levator ani, Compressor urethrae, and occasionally a few fibres of the Accelerator 
urinae. 

THE PELVIS (Figs. 170, 171). 

The pelvis is stronger and more massively constructed than either the cranial 
or thoracic cavity; it is a bony ring, interposed between the lower end of the verte- 
bral column, which it supports, and the lower extremities, upon which it rests. 
It is composed of four bones — the two ossa innominata, which boiuid it on either 
side and in front, and the sacrum and cocc3rx, which complete it behind. The 
pelvis is divided by an oblique plane passing through the prominence of the 
sacrum, the iliopectineal line, and the upper margin of the syinphysis pubis 
into the false and true pelvis. 

The False Pelvis {pelvis major) is the expanded portion of the pelvic cavity 
which is situated above this plane. It is bounded on each side by the ossa ilii; 
in front it is incomplete, presenting a wide interval between the spinous proces.ses 
of the ilia on either side, which is filled up in the recent state by the parietes of 
the abdomen; behind, in the middle line, is a deep notch. This broad, shallow 
cavity is fitted to support the intestines and to transmit part of their weight to 
the anterior wall of the abdomen, and is, in fact, really a portion of the abdominal 
cavity. The term false pelvis is incorrect, and this space ought more properly to 
be regarded as part of the hypogastric and iliac regions of the abdomen. 

The True Pelvis (pelvis minor) is that part of the pelvic cavity which is 
situated below the iliopectineal line. It is smaller than the false pelvis, but its 
walls are more perfect. For convenience of description it is divided into a superior 
circumference, or inlet, an inferior circumference, or outlet, and a cavity. 

Tiie superior circumference, or inlet (apertura pelvis superior), forms the brim 
of the pelvis, the included space being called the inlet. It is formed by the ilio- 
pectineal line, completed in front by the crests of the pubic bones, and behind 
by the anterior margin of the base of the sacrum and sacrovertebral angle. Tlie 
inlet of the pelvis is somewhat heart-shaped, obtusely pointed in front, diverging 
on either side, and encroached upon behind by the projection forward of the 
promontory of the sacrum. It has three principal diameters — antero-posterior 
(sacropubic), transverse, and oblique. The antero-posterior or conjugate diameter 
(conjugata) extends from the sacrovertebral angle to the symphysis pubis. Its 
average measurement is four inches in the male and four and three-fifths inches 
in the female. The transverse diameter {diameter transversa) extends across 
the greatest width of the inlet, from the middle of the brim on one side to the 



216 SPECIAL ANATOMY OF THE SKELETON 

same point on the opposite; its average measurement is five inches in the male, 
five and one-fourth inches in the female. The oblique diameter (diameter ohliqua) 
extends from the margin of the pelvis, corresponding to the iliopectineal eminence 




170.— Male pelvis (adult). 



on one side, to the sacroiliac articulation on the opposite side; its average measure- 
ment is four and one-fourth inches in the male and five in the female. 

The cavity of the true pelvis is bounded in front by the symphysis pubis; behind, 
by the concavity of the sacrum and coccyx, vt'hich, curving forward above and 




Fig. 171. — Female pelvis (adult). 



belovv^, contracts the inlet and outlet of the canal; and laterally it is bounded by 
a broad, smooth, quadrangular surface of bone, corresponding to the inner surface 
of the body of the ischium and that part of the ilium which is below the ilio- 



THE PEL Vm 217 

pectineal line. The cavity is sliallow in front, measuring at the symphysis an 
inch and a half in depth, three inches and a half in the middle, and four 
inches and a half posteriorly. From this description it will be seen that the cavity 
of the pelvis is a short, curved canal, considerably deeper on its posterior thaii 
on its anterior wall. This cavity contains, in the recent subject, the rectum, 
bladder, and some of the organs of generation. The rectum is placed at the back 
of the pelvis, and corresponds to the curve of the sacrococcygeal segment of the 
vertebral column; the bladder in front, behind the symphysis pubis. In the female 
the uterus and vagina occupy the interval between these viscera. 

The lower circumference is very irregular; the space enclosed by it is called 
the outlet (apertura pelvis inferior). It is bounded by three prominent emi- 
nences — one posterior, formed by the point of the coccyx; and one on each side, 
the tuberosities of the ischia. These eminences are separated by three notches; 
one in front, the pubic arch (arciis pubis), formed by the convergence of the rami 
of the ischia and pubic bones on each side. The other notches, one on each side, 
are formed by the sacrum and coccyx behind, the ischium in front, and the ilium 
above ; they are called the sacrosciatic notches ; in the natural state they are converted 
into foramina by the lesser and greater sacrosciatic ligaments. In the recent 
state, when the ligaments are in situ, the oudet of the pelvis is lozenge-shaped, 
bounded in front by the subpubic ligament and the rami of theos pubis and ischium; 
on each side by the tuberosities of the ischia; and behind by the great sacrosciatic 
ligaments and the tip of the coccyx. 

The diameters of the outlet of the pelvis are two, antero-posterior and trans- 
verse. The antero-posterior diameter extends from the tip of the coccyx to the 
lower part of the symph}'sis pubis; its average measurement is three and three- 
quarter inches in the male and four and one-half inches in the female. The 
antero-posterior diameter varies with the length of the coccyx, and is capable 
of increase or diminution on account of the mobility of that bone. During labor 
the coccyx may be bent back so that the conjugate is increased one inch, or even 
one and one-fourth inches. The transverse diameter extends from the posterior 
part of one ischiatic tuberosity to the same point on the opposite side; the average 
measurement is three and one-half inches in the male and four and three-fourths 
in the female.' 

Position of the Pelvis. — In the erect posture the pelvis is placed obliquely with 
regard to the trunk of the body; the bony ring, which forms the brim of the true 
pelvis, is placed so as to form an angle of about 60 to 65 degrees with the ground 
on which we stand (inclinatio pelvis). The pelvic surface of the symphysis 
pubis looks upward and backward, the concavity of the sacrum and coccyx down- 
ward and forward, the base of the sacrum in well-formed female bodies being 
nearly four inches above the upper border of the symphysis pubis, and the apex 
of the coccyx a little more than half an inch above its lower border. In conse- 
quence of the obliquity of the pelvis the line of gravity of the head, which passes 
through the middle of the odontoid process of the axis and through the points 
of junction of the curves of the vertebral column to the sacrovertebral angle, 
descends toward the front of the cavity, so that it bisects a line drawn transversely 
through the middle of the heads of the thigh bones. And thus the centre of gravity 
of the head is placed immediately over the heads of the thigh bones on which the 
trunk is supported. 

' The measurements of the pelvis given above are, I believe, fairly accurate, but different measurements are 
given by various authors, no doubt due in a great measure to differences in the physique and stature of the 
population from whom the measurements have been taken. The accompanying table has been formulated to 
show the measurements of the pelvis which are adopted by many obstetricians. — [Editor.] 



Diameters of the True Pelvis in Woman. 
Antero-posterior. Oblique. Transrerse. 

Of inlet . . 4';5 inches (118 mm.) 5 inches (127 mm.) SVt inches (135 i 

Of outlet. . 4'/.., inches (115 mm.) 4»;i inches (120 i 



218 



SPECIAL ANATOMY OF THE SKELETON 



Axes of the Pelvis (Fig. 172). — The plane of the inlet of the true pelvis will 
be represented by a line drawn from the base of the sacrum to the upper margin 
of the symphysis pubis. A line carried at right angles with this at its middle 
would correspond at one extremity with the umbilicus, and at the other with the 
middle of the coccyx; the axis of the inlet is therefore directed downward and 
backward. The axis of the outlet, prolonged upward, would touch the base of 

the sacrum, and is therefore directed downward 
and forward. The axis of the cavity is curved 
like the cavity itself; this curve corresponds to 
the concavity of the sacrum and coccyx, the 
extremities being indicated by the central points 
of the inlet and outlet. A knowledge of the 
direction of these axes serves to explain the 
course of the fetus in the passage through the 
pelvis during parturition. 

Differences between the Male and Female 

Pelvis. — The female pelvis, looked at as a whole, 

is distinguished from the male by the bones 

being more delicate, by its width being greater 

and its depth smaller. The whole pelvis is less 

massive, and its bones are lighter and more 

slender, and its muscular impressions are slightly 

marked. The iliac fossae are shallow, and the 

anterior iliac spines widely separated; hence the 

greater prominence of the hips. The inlet in 

the female is larger than in the male; it is more 

nearly circular, and the sacrovertebral angle 

projects less forward. The cavity is shallower and wider; the sacrum is shorter, 

wider, and less curved; the obturator foramina are triangular, and smaller in size 

than in the male. The outlet is larger and the coccyx more movable. The 




Plane 0/ 



outlet. 



Fig. 172. — Vertical section of the pelvis, 
with lines indicating the axis of the pelvis. 




Fig. 173. — Diameters of the pelvic inlet in the female. 



spines of the ischia project less inward. The tuberosities of the ischia aud the 
acetabula are wider apart. The pubic arch is wider and more rounded than in 
the male, where it is an angle rather than an arch. In consequence of this the 



THE PELVIS 



219 



width of the fore part of the pelvic outlet is much increased and the passage 
of the fetal head facilitated. 

The size of the pelvis varies not only in the two sexes, but also in different 
members of the same sex. This does not appear to be influenced in any way by 
the height of the individual. Women of short stature, as a rule, have broad 
pelves. Occasionally the pelvis is equally contracted in all its dimensions, so 
much so that all its diameters measure an inch less than the average, and this 
even in women of average height and otherwise well formed. The principal 
divergences, however, are foimd at the inlet, and affect the relation of the antero- 
posterior to the transverse diameter. Thus we may have a pelvis the inlet of 
which is elliptical either in a transverse or antero-posterior direction; the trans- 
verse diameter in the former and the antero-posterior in the latter greatly exceeding 
the other diameters. Again, the inlet of the pelvis in some instances is seen to 
be almost circular. The same differences are found in various races. European 
women are said to have the most roomy pelves. That of the negress is smaller, 
circular in shape, and with a narrow pubic arch. The Hottentots and Bushwomen 
possess the smallest pelves. 




Fig. 174. — Diameters of the pelvic outlet in the female. 

In the fetus and for several years after birth the pelvis is small in proportion 
to that of the adult. The cavity is deep and the projection of the sacrovertebral 
angle less marked. The generally accepted opinion that the female pelvis does 
not acquire its sexual characters until after puberty has been shown by recent 
observations^ to be erroneous, the characteristic differences between the male and 
female pelvis being distinctly indicated as early as the fourth month of fetal life. 
At birth these differences are distinct (Romiti), the female pelvis possessing less 
straight ilia, a broader subpubic arch, and less height than the male. 

Surface Form.— The pelvic bones are so thickly covered with muscles that it is only at cer- 
tain points that they approach the surface and can be feU through the skin. In front, the anterior 
superior spinous process is easily recognized; a portion of it is subcutaneous, and in thin sub- 
jects may be seen to stand out as a prominence at the outer extremity of the fold of the groin, 
in fat subjects its position is marked by an oblique depression among the surrounding fat, 
at the bottom of which the bony process may be felt. Proceeding upward and outward from 
this process, the crest of the ilium may be traced throughout its whole length, sinuously curved. 
It is represented, in muscular subjects, on the surface, by a groove or furrow, the iliac furrow, 
caused by the projection of fleshy fibres of the External oblique muscles of the abdomen ; the 

niik.. Band ix and x; and Arthur Thomson, Journ.al of .Anatomy and 



220 SPECIAL ANATOMY OF THE SKELETON 

iliac furrow lies slightly below the level of the crest. It terminates behind in the posterior supe- 
rior spinous process, the position of which is indicated by a slight depression on a level with the 
spinous process of the second sacral vertebra. Between the two posterior superior spinous 
processes, but at a lower level, is to be felt the spinous process of the third sacral vertebra (see 
page 68). Another part of the bony pelvis easily accessible to touch is the tuberosity of the 
ischium, situated beneath the gluteal fold, and, when the hip is flexed, it is easily felt, as it is then 
to a great extent uncovered by muscle. Finally, the spine of the os pubis can always be readily 
felt, and constitutes an important surgical guide, especially in connection with the subject of 
hernia. It is nearly in the same horizontal line with the upper edge of the great trochanter. In 
thin subjects it is very apparent, but in the obese it is obscured by the pubic fat. It can, however, 
be detected by everting the thigh and following up the tendon of origin of the Adductor longus 
muscle. 

Applied Anatomy. — There is arrest of development in the bones of the pelvis in cases of 
extroversion of the bladder; the anterior part of the pelvic girdle being deficient, the bodies of the 
pubic bones imperfectly developed, and the symphysis absent. The pubic bones are separated 
to the extent of from two to four inches, the superior rami shortened and directed forward, and 
the obturator foramen diminished in size, narrowed, and turned outward. The iliac bones are 
straightened out more than normal. The sacrum is very peculiar. The lateral curve, instead of 
being concave, is flattened out or even convex, with the iliosacral facets turned more outward 
than normal, while the vertical curve is straightened.' 

Fractures of the pelvis are divided into fractures of the false pelvis and of the true pelvis. Frac- 
tures of the false pelvis vary in extent: a small portion of the iliac crest may be broken or one of 
the spinous processes may be torn off, and this may be the result of muscular action; or the 
bone may be extensively comminuted. This latter accident is the result of some crushing vio- 
lence, and may be complicated with fracture of the true pelvis. These cases may be accompanied 
by injury to the intestine as it lies in the hollow of the bone, or to the iliac vessels as they course 
along the margin of the true pelvis. Fractures of the true pelvis generally occur through the 
ascending ramus of the os pubis and the ramus of the ischium, as this is the weakest part of the 
bony ring,, and may be caused either by crushing violence applied in an antero-posterior direction, 
when the fracture occurs from direct force, or by compression laterally, when the acetabula are 
pressed together, and the bone gives way in the same place from indirect violence. Occasionally 
the injury may be double, a break occurring on both sides of the body. In fracture of. the true 
pelvis the contained viscera are liable to be damaged; the small intestines, the urethra, the bladder, 
the rectum, the vagina, and even the uterus, in the female, have all been lacerated by a dis- 
placed fragment. Fractures of the acetabulum are occasionally met with; either a portion of 
the rim may be broken off, or a fracture may take place through the bottom of the cavity, and the 
head of the femur may be driven inward and project into the pelvic cavity. Separation of the 
Y-shaped cartilage at the bottom of the acetabulum may also occur in the young subject, 
dispersing the bone into its three anatomical portions. 

The sacrum, is seldom broken. The cause is direct violence — i. e., blows, kicks, or falls on the 
part. The lesion may be complicated with injury to the nerves of the sacral plexus, leading 
to paralysis and loss of sensation in the lower extremity or to incontinence of feces from paralysis 
of the Sphincter ani. 

Fracture of the coccyx is a very rare injury, but does occasionally take place. Some sup- 
posed dislocations of this bone have been fractures and so have some of the cases diagnosticated 
as coccygodynia. A fracture of the coccyx is due to direct force. 

The pelvic bones often undergo important deformity in rhachiti-s, the effect of which in the 
adult woman may interfere seriously with childbearing. The deformity is due mainly to the 
weight of the spine and trunk, which presses on the sacrovertebral angle and greatly increases 
it, so that the antero-posterior diameter of the pelvis is diminished. But, in addition to this, 
the weight of the viscera on the venter ilii causes the ilia to expand and the tuberosities of the 
ischia to incurve. In osteomalacia also great deformity may occur. The weight of the trunk 
causes an increase in the sacrovertebral angle and a lessening of the antero-posterior diameter 
of the inlet, and at the same time the pressure of the acetabula on the heads of the thigh bones 
causes these cavities, with the adjacent bone, to be pushed upward and backward, so that the 
oblique diameters of the pelvis are also diminished, and the cavity of the pelvis assumes a tri- 
radiate shape, with the symphysis pubis pushed forward. 

THE THIGH. 

The thigh is that portion of the lower extremity which is situated between the 
pelvis and the knee. It consists in the skeleton of a single bone, the fenmr. 

1 Wood, Heath's Dictionary of Practical Surgery, i, 426. 



THE FE31VB, OR THIGH BONE 



221 



The Femur, or Thigh Bone 

(Figs. 175, 177). 

The femur (femur) is tiie long- 
est,' largest, and strongest bone 
in the skeleton, and almost per- 
fectly cylindrical throughout the 
greater part of its extent. In the 
erect posture it is not vertical, 
being separated from its fellow 
above by a considerable interval, 
which corresponds to the entire 
breadth of the pelvis, but inclin- 
ing gradually downward and in- 
ward, so as to approach its fellow 
toward its lower part, for the 
purpose of bringing the knee-joint 
near the line of gravity of the 
body. The degree of this incli- 
nation varies in different persons, 
and is greater In the female than 
the male, on account of the greater 
breadth of the pelvis. The femur, 
like other long bones, is divisible 
into a shaft and two extremities. 

The Upper or Proximal Ex- 
tremity presents for examination 
S head, a neck, and a greater and 
a lesser trochanter. 

The head {caput femor is) ,v\\\ch. 
is globulai^ and forms rather more 
than a hemisphere, is directed up- 
ward, inward, and a little forward, 
the greater part of its convexity 
being above and in front. Its 
surface is smooth, coated with 
hyaline cartilage in the recent 
state, except at a little behind and 
below its centre, where there is 
an ovoid depression {fovea capitis 
femoris), for the attachment for 
the ligamentum teres. 

The neck {collum femoris) is 
a flattened pyramidal process of 
bone which connects the head 
with the shaft. It varies in length 
and obliquity at various periods in 
life and under different circum- 
stances. The angle is widest in 
infancy, and becomes lessened 
during growfh, so that at puberty 
it forms a gehtle curve from the 



1 In a man six fee^ high it measures eighteen 
inches — one-fourth of the whole body stature. 




DepreMion for 

LIGAMENTUM TERES. 



'"■e/- CoiliW 



"Ve. 
Fig. 175. — Right femu 



Anterior surfacei 



'222 



SPECIAL ANATOMY OF THE SKELETON 



axis of the shaft. In the adult it forms an angle of about 125 degrees with the 
shaft, but varies in inverse proportion to the development of the pelvis and the 
stature. In consequence of the prominence of the hips and widening of the pelvis 
in the female, the neck of the thigh bone forms more nearly a right angle with the 
shaft than it does in the male. The neck is flattened from before backward, 
contracted in the middle, and broader at its outer extremity, where it is connected 
with the shaft, than at its summit, where it is continuous with the head. The 
vertical diameter of the outer half is increased by the thickening of the lower edge, 
which slopes downward to join the shaft at the lesser trochanter; as a result of 
this the outer half of the neck is flattened from before backward, and its vertical 
diameter measures one-third more than the antero-posterior. The inner half 
is smaller and of a more circular shape. The anterior surface of the neck is per- 
forated by numerous vascular foramina. The posterior surface is smooth, and is 
broader and more concave than the anterior; it gives attachment to the posterior 
part of the capsular ligament of the hip-joint, about half an inch above the 
posterior intertrochanteric line. The superior border is short and thick, and ter- 
minates externally at the great trochanter; its surface is perforated by large 
foramina. The inferior border, long and narrow, curves a little backward, to 
terminate at the lesser trochanter. 



Obturator intemus and GemelU 
Pip if 01 nns 

4'^^ Insertion of Obturator 
" c^&^ extemus 




Greater trochanter 



Fig. 176. — Upper extremity of the femur \iewed from behind and abov 



The trochanters are prominent processes of bone which afford leverage to the 
muscles which rotate the thigh on its axis. They are two in number, the greater 
and the lesser. 

The greater trochanter (trochanter major) is a large, irregular, quadrilateral emi- 
nence, situated at the outer side of the neck, at its junction with the upper part of 
the shaft. It is directed a little outward and backward, and in the adult is about 
three-quarters of an inch lower than the head. It presents for examination 
two surfaces and four borders. The external surface, quadrilateral in form, is 
broad, rough, convex, and marked by a prominent diagonal impression, which 
extends from the posterior superior to the anterior inferior angle, and serves for 
the attachment of the tendon of the Gluteus medius. Above the impression is 
a triangular surface, sometimes rough for part of the tendon of the same muscle, 
sometimes smooth for the interposition of a bursa between that tendon and the 
bone. Below and behind the diagonal line is a smooth, triangular surface, 
over which the tendon of the Gluteus maximus muscle plays, a bursa being inter- 
posed. The internal surface is of much less extent than the external, and presents 



THE FEMUR, OR THIGH BONE 



223 



at its base a deep depression, the 
digital or trochanteric fossa {fossa 
Irochauterica), for the attachment 
of the tendon of the Obturator 
externus muscle; above and in 
front of this an impression for 
the attachment of the Obtura- 
tor internus and Gemelli. The 
superior border is free; it is thick 
and irregular, and marked near 
the centre by an impression, which 
extends onto the internal surface, 
for the attachment of the Pyri- 
formis. The inferior border cor- 
responds to the point of junction 
of the base of the trochanter with 
the outer surface of the shaft; it 
is marked by a rough, prominent, 
slightly curved ridge, which gives 
origin to the upper part of the 
Vastus externus muscle. The 
anterior border is prominent, 
somewhat irregular, as well as the 
surface of bone immediately be- 
low it ; it affords attachment at its 
outer part to the Gluteus mini- 
mus. The posterior border is veiy 
prominent, and appears as a free, 
rounded edge, which forms the 
back part of the digital fossa. 

The lesser trochanter (trochan- 
ter minor) is a conical eminence 
which varies in size in different 
subjects; it projects from the lower 
and back parts of the base of the 
neck. Its base is triangular, and 
connected with the adjacent parts 
of the bone by three well-marked 
borders; two of these are above 
— the internal border, continuous 
with the lower border of the neck, 
the external border, with the pos- 
terior intertrochanteric line — 
while the inferior border is con- 
tinuous with the middle division 
of the linea aspera. Its summit, 
which is directed inward and 
backward, is rough and gives 
insertion to the tendon of the 
Iliopsoas. The Iliacus is also 
inserted into the shaft below 
the lesser trochanter between the 
Vastus internus in front and the 
Pectineus behind. 




^ Groove for tendon of 



Tic 177. — Eight femur Posterior surface. 



224 



SPECIAL ANATOMY OF THE SKELETON 



A well-marked prominence of variable size, which projects from the upper and 
front part of the neck at its junction with the great trochanter, is called the 
tubercle of the femur; it is the point of meeting of five muscles — the Gluteus mini- 
mus externally, the Vastus externus below, and the tendon of the Obturator internus 
and Gemelli internally. Running obliquely downward and inward from the 
tubercle is the spiral line of the femur, or anterior intertrochanteric line (linea inter- 
Irochanierica); it winds around the inner side of the shaft, below the lesser tro- 
chanter, and terminates about two inches below this eminence in the linea aspera. 
Its upper half is rough, and affords attachment to the iliofemoral ligament of the 
hip-joint; its lower half is less prominent, and gives origin to the upper part of the 
Vastus internus. Running obliquely downward and inward from the summit 
of the great trochanter on the posterior surface of the neck is a very prominent, 
well-marked ridge, the posterior intertrochanteric 
a, .& line (crista intertrochavf erica). Its upper half 

forms the posterior border of the great tro- 
chanter, and its lower half runs down\\"ard and 
inward to the upper and back part of the lesser 
trochanter. A slight ridge sometimes com- 
mences about the middle of the posterior intertro- 
chanteric line, and passes vertically downward 
for about two inches along the back part of the 
shaft; it is called the linea quadrati, and gives 
attachment to the Quadratus femoris and a few 
fibres of the Adductor magnus muscles.' 

The Shaft (corpus femoris). — The shaft, almost 
cylindrical in form, is a little broader above than 
in the centre, and somewhat flattened below, from 
before backward. It is slightly arched, so as to 
be convex in front and concave behind, where it 
is strengthened by a prominent longitudinal ridge, 
the linea aspera. It presents for examination 
three borders, separating three surfaces. Of 
the three borders, one, the linea aspera, is poste- 
rior; the other two are placed laterally. 

The linea aspera (Fig. 178) is a prominent 
longitudinal ridge or crest, on the middle third 
of the bone, presenting an external lip (labium 
laterale), an internal lip (labium mecliale), and a 
rough intermediate space. Above, this crest is 
prolonged by three ridges. The most external 
ridge is very rough, and is continued almost 
vertically upward to the base of the great trochanter. It is sometimes termed 
the gluteal ridge (tuberositas glutaea), and gives attachment to part of the Gluteus 
maximus muscle; its upper part is sometimes elongated into a roughened 
crest, on which is a more or less well-marked, rounded tubercle, a rudimental 
third trochanter (trochanter tertius). The middle ridge (linea pectinea), the least 
distinct, is continued to the base of the lesser trochanter, and the internal ridge is 
lost above in the spiral line of the femur. Below, the linea aspera is prolonged 
by two ridges, which pass to the condyles and enclose between them a triangular 
space, the popliteal surface (planum popliteum), upon which rests the popliteal 
artery. Of these two ridges, the outer one is the more prominent, and descends 
to the summit of the outer condyle. The inner one is less marked, especially at 




ADDUCTOR 
TUBERCLE 

Fig. 178. — Diagram of linea aspera of the 
right femur, {.\fter Birmingham.) 



' Generally there is merely a slight thickening about the centre of the intertrochanteric line, marking the point 
of attachment of the Quadratus femoris. This is termed by some anatomists the tubercle of the Quadratus. 



THE FEMUR, OR THIGH BONE 225 

its upper part, where it is crossed by the femoral artery. It terminates, below, 
at the summit of the internal condyle, in a small tul^ercle, the adductor tubercle, 
which affords attachment to the tendon of the Adductor magnus. To the inner 
lip of the linea aspera and its inner prolongation above and below arises the 
Vastus internus, and to the outer lip and its outer prolongation above arises the 
Vastus externus. The Adductor magnus is attached to the linea aspera, to its 
outer prolongation above and its inner prolongation below. Between the Vastus 
externus and the Adductor magnus are attached two muscles — viz., the Gluteus 
maximus above, and the short head of the Biceps femoris below. Between the 
Adductor magnus and the Vastus internus four muscles are attached — the Iliacus 
and Pectineus above, the Adductor brevis and Adductor longus below (Fig. 178). 
A little below the centre of the linea aspera is the nutrient foramen, the orifice of 
the nutrient canal, which is directed obliquely upward (proximally). 

The two lateral borders of the femur are only slightly marked, the outer one ex- 
tending from the anterior inferior angle of the great trochanter to the anterior 
extremity of the external condyle; the inner one from the spiral line at a point 
opposite the lesser trochanter, to the anterior extremity of the internal condyle. 
The internal border marks the limit of origin of the Crureus muscle internally. 

The anterior surface includes that portion of the shaft which is situated bet\\een 
the two lateral borders. It is smooth, convex, broader above and below than in 
the centre, slightly twisted, so that its upper part is directed forward and a little 
outward, its lower part forward and a little inward. From the upper three-fourths 
of this surface the Crureus takes origin; the lower fourth is separated from the 
muscle by the intervention of the synovial membrane of the knee-joint and a bursa, 
and affords origin to the Subcrureus to a small extent. 

The external surface includes the portion of bone between the external border 
and the outer lip of the linea aspera; it is continuous above with the outer surface 
of the great trochanter, below with the outer surface of the external condyle; 
from its upper three fourths arises the outer portion of the Crureus muscle. 

The internal surface includes the portion of bone between the internal border 
and the inner lip of the linea aspera; it is continuous above with the lower border 
of the neck, below with the inner side of the internal condyle; it is covered by the 
Vastus internus muscle. 

Lower or Distal Extremity. — The lower extremity, larger than the upper, 
is of a cuboidal form, flattened from before backward, and divided into two large 
eminences, the condyles, by an interval which presents a smooth depression in 
front called the trochlea {fames ■patellaris), and a notch of consideraljle size behind — 
the intercondyloid notch (fossa intercondyloidea). The external condyle (condyles 
lateralis) is the more prominent anteriorly, and is the broader both in the antero- 
posterior and transverse diameters. The internal condyle (condylus medialis) is 
the longer, and more prominent inferiorly. This difference in the length of the 
two condyles is only observed when the bone is perpendicular and depends upon 
the obliquity of the thigh bones, in consequence of their separation above at the 
articulation with the pelvis. If the femur is held obliquely, the surfaces of the 
two condyles will be seen to be nearly horizontal. The two condyles are directly 
continuous in front, and form a smooth, trochlear surface, tjie trochlea. The 
trochlea and the inferior surface of the condyles constitute the articular surface 
of the lower end of the femur, and are covered by hyaline cartilage in the recent 
state. The trochlea articulates with the patella. It presents a median groove, 
which extends downward and backward to the intercondyloid notch; and two 
lateral convexities, of which the external is the broader, more prominent, and pro- 
longed farther upward upon the front of the outer condyle. The external border 
of this articular surface is also more prominent, and ascends higher than the 
internal one. The inferior surfaces of the condyles are convex from side to side 

15 



226 ^FECIAL ANATOMY OF THE SKELETON 

and from before backward, and articulate with the corresponding surfaces of 
the tibia. They are marked off from the trochlea by two irregular grooves. 
The outer groove runs obliquely outward and forward from the anterior extremity 
of the intercondyloid notch to the outer side of the external condyle. The inner 
is less well marked and placed farther forward than the one on the external 
condyle; it extends obliquely inward and backward. In the grooves the semilunar 
cartilages fit when the knee is extended. The opposed surfaces of the condyles 
form the lateral walls of the intercondyloid notch. 



_ / ■ groove. 



^ .Inner tuberosity. 
» ^Semilunar area. 




Outer tuberosity. . ,- , 



y 



Fig. 179. — Lower extremity of riglit femur viewed from below. 

The outer surface of the external condyle presents, a little behind its centre, 
an eminence, the outer tuberosity (epico7idylus lateralis); it is less prominent 
than the inner tuberosity, and gives attachment to the external lateral ligaments 
of the knee. Immediately beneath it is the popliteal groove, which commences 
at a depression a little behind the centre of the lower border of this surface; 
the front part of this depression gives origin to the Popliteus muscle, the tendon 
of which is lodged in the groove during flexion of the knee. The groove is smooth, 
covered with hyaline cartilage in the recent state, and runs upward and back- 
ward to the posterior extremity of the condyle. The posterior extremity is con- 
vex and smooth; just above and to the outer side of the articular surface is a de- 
pression for the tendon of the outer head of the Gastrocnemius, above which is 
the origin of the Plantaris. 

The inner surface of the inner condyle presents a convex eminence, the inner 
tuberosity {epicondyliw medialis) , rough, for the attachment of the internal lateral 
ligament. Just above the articular surface of this condyle, behind, is a depres- 
sion for the tendon of origin of the inner head of the Gastrocnemius. 

The intercondyloid notch is bounded laterally by the opposed surfaces of the 
.condyles, and lodges the crucial ligaments of the knee-joints. The inner wall 
of the notch at its front part has attached to it the posterior crucial ligament. 
The external wall at its upper and back part affords attachment to the anterior 
crucial ligament. Above, it is separated from the popliteal surface by a ridge — 
the linea inter condyloidea. 

Structure. — ^The shaft of the femur is a cylinder of compact tissue, hollowed by a large med- 
ullary canal. The cyhnder is of great thickness and density in the middle third of the shaft, 
where the bone is narrowest and the medullary canal well formed; but above and below this 
the cavity gradually becomes smaller, owing to a separation of the layers of the bone into cancelli, 
which project into the medullary canal and finally obliterate it, so that the upper and lower 
ends of the shaft, and the articular extremities more especially, consist of cancellated tissue 
invested by a thin, compact layer. 

The arrangement of the cancelli in the ends of the femur is remarkable. In the upper end they 
are arranged in two sets. One, starting from the top of the head, the upper surface of the neck. 



THE FEMUR, OR THIGH BONE 



227 



and the great trochanter, converge to the inner circumference of the shaft (Figs. ISO and ISl); 
these are placed in the direction of greatest pressure, and serve to support the vertical weight 
of the body. The second set are planes of lamellae intersecting the former nearly at right angles, 
and are situated in the line of the greatest tension — 
that is to say, along the lines in which the muscles and 
ligaments exert their traction. In the head of the 
bone these planes are arranged in a cur\'ed form, in 
order to strengthen the bone when exposed to pressure 
in all directions. In the midst of the cancellous tis- 
sue of the neck is a vertical plane of compact bone, 
the femoral spur (calcar femorale), which commences 
at the point where the neck joins the shaft just exter- 
nal to the lesser trochanter, and extends in the direc- 
tion of the digital fossa (Fig. 1S2). This materially 
strengthens this portion of the bone. Another point in 
connection with the structure of the neck of the femur 
requires mention, especially on accoimt of its influence 
on the production of fracture in this situation. It wdll 
be noticed that a considerable portion of the great 
trochanter lies behind the level of the posterior sur- 
face of the neck; and if a section be made tlirough 
the trochanter at this level, it will be seen that the 
posterior wall of the neck is prolonged into the tro- 
chanter. This prolongation is termed by Bigelow the true neck,' and forms a thin, dense 
plate of bone, which passes beneath the posterior intertrochanteric ridge toward the outer sur- 
face of the bone. In the lower end the cancelU spring on all sides from the inner surface of the 




Fig. 180. — Scheme showing disposition of 
principal cancellous lamellEe in upper extrem- 
ity of femur. 



Epiphyseal line. 




Fig. ISl. — Longitudinal section of head and necic of femur. 

cylinder, and descend in a perpendicidar direction to the articular surface, the cancelli being 
strongest and ha\'ing a more accurately perpendicular course above the condyles. In addition 



the Hip, p. 121. 



228 



SPECIAL ANATOMY OF THE SKELETON 



to this, however, horizontal planes of cancellous tissue are to be seen, so that the spongy tissue in 
this situation presents an appearance of being mapped out into a series of rectangular areas. 

Articulations. — With tkree bones — the os innominatum, tibia, and patella. 

Development (Fig. 1 S3). — The femur is developed from five centres — one for the shaft, one 
for each extremity, and one for each trochanter. Of all the long bones, except the clavicle, it is 
the first to show traces of ossification; this commences in the shaft, at about the seventh week of 
fetal life, the centres of ossification in the epiphyses appearing in the following order: First, in 
the lower end of the bone, at the ninth month of fetal life' (from this the condyles and tuber- 
osities are formed) ; in the head at the end of the first year after birth ; in the great trochanter, 
during the foiu'th year; and in the lesser trochanter, between the thirteenth and fourteenth years. 
The order in which the epiphyses are joined to the shaft is the reverse of that of their appearance; 
their junction does not commence until after puberty, the lesser trochanter being first joined, 
then the great, then the head, and lastly the inferior extremity (the first in which ossification 
commenced), which is not united until the twentieth year. Because of this late union, the lower 
extremity of the femur has been called the "growing end" of the bone, and early arrest of ossifi- 
cation here results in more or less marked diminution of stature. 



Great trochanter. 



^ Digital fossa. 




Appears at Ifth 
year; joins shaft ^ 
ahout 18th year. i= 




'^ Joins shaft at SOth 
9th mon ' i ^J^ J^^ year. 
(fetaC). \=f 

Lower extremity. 



J^iG, 182. — Calcar femorale. 



Attachment of Muscles.— To tiventy-three. To the great trochanter: the Gluteus medius, 
■Gluteus minimus, Pyriformis, Obturator internus. Obturator externus, Gemellus superior, 
and Gemellus inferior. To the lesser trochanter: the Psoas magnus and the Iliacus below it. 
To the shaft: the Quadratus femoris, Vastus externus, Gluteus maximus, short head of the 
Biceps femoris. Vastus internus. Adductor magnus, Pectineus, Adductor brevis. Adductor 
longus, Crureus, and Subcrureus. To the condyles: the Gastrocnemius, Plantaris, and 
Popliteus. 

Surface Form. — The femur is covered with muscles, so that in fairly muscular subjects the 
shaft is not to be detected through its fleshly covering, and the only parts accessible to the touch 
are the outer surface of the great trochanter and the lower expanded end of the bone. The 
external surface of the great trochanter may be felt, especially in certain positions of the limb. Its 
position is generally indicated by a depression, owing to the thickness of the Gluteus medius and 



^ This is said to be the only epiphysis in which ossification begins before birth; though, according to 
observers, the centre for the upper epiphysis of the tibia also appears before birth. 



THE FEMUR, OB THIGH BONE 229 

minimus, which project above it. When, however, the thigh is flexed, and espeeiully if crossed 
over the opposite one, the trochanter produces a blunt eminence on the surface. The upjjer 
border is about on a hne with the spine of the os pubis, and its exact level is indicated by a line 
drawn from the anterior superior spinous process of the ilium, over the outer side of the liip, 
to the most prominent point of the tuberosity of the ischium. This is known as N§laton's line. 
The outer and inner condyles of the lower extremity may easily be felt. The outer one is 
more subcutaneous than the inner one, and readily felt. The tuberosity on it is comparatively 
little developed, but can be more or less easily recognized. The inner condyle is more thickly 
covered, and this gives a general convex outline to this part, especially when the knee is flexed. 
The tuberosity on it is easily felt, and at the upper part of the condyle the sharp tubercle for the 
insertion of the tendon of the Adductor magnus can be recognized without difficulty. Occa- 
sionally, exostoses develop in the tendon of insertion of the Adductor magnus; these are the 
"rider's hones" of cavalry soldiers and horsemen (pp. 360, 515). When the knee is flexed, and 
the patella situated in the interval between the condyles and the upper end of the tibia, a part 
of the trochlear surface of the femur can be made out above the patella. 

Applied Anatomy. — There are one or two points about the ossification of the femur bear- 
ing on practice to which allusion must be made. It has been stated above that the lower end 
of the femur is the only epiphysis in which ossification has commenced at the time of birth. 
The presence of the ossific centre in newly born children found dead is, therefore, a proof that 
the child has arrived at the full period of uterogestation. However, according to Hartman, 
at term this centre is absent in 12 per cent, of cases. The position of the epiphyseal line should 
be carefully noted. It is on a level with the adductor tubercle, and the epiphysis does not, 
therefore, form the whole of the cartilage-clad portion of the lower end of the bone. It is essen- 
tial to bear this point in mind in performing excision of the knee, since growth in length of the 
femur takes place chiefly from the lower epiphysis, and any interference with the epiphyseal 
cartilage in a young child would involve such ultimate shortening of the limb, from want of 
growth, as to render it almost useless. Separation of the loiver epiphysis may take place up to 
the age of twenty, at which time it becomes completely joined to the shaft of the bone; but, as 
a matter of fact, few cases occur after the age of sixteen or seventeen. The epiphysis of the head 
of the femur is of interest principally on account of its being the seat of origin of a large number 
of cases of tiiberciilous disease of the hip-joint. The disease commences in the majority of cases 
in the highly vascular and growing tissue in the neighborhood of the epiphysis, and from here 
extends into the joint. In the condition known as coxa tarn the head of the femur falls to a lower 
level than normal. The angle between the neck and shaft is greatly diminished and may become 
a right ^ngle, or the head may actually descend to a lower level than that of the trochanter. The 
neck is also bent with a convexity forward ; coxa vara is due to rachitis. 

Fractures of the femur are divided, like those of the other long bones, into fractures of the 
upper end, of the shaft, and of the lower end. The fractures of the upper end may be classi- 
fied into (1) fracture of the neck; (2) fracture at the junction of the neck with the great trochanter; 
(.3) fracture of the great trochanter; and (4) separation of the epiphysis, either of the head or 
the great trochanter. The first of these, fracture of the neck, is usually termed intracapsular 
fracture, but this is scarcely a correct designation, as, owing to the attachment of the capsular 
ligament, the fracture may be partly within and partly without the capsule, when the fracture 
occurs at the lower part of the neck. It generally occurs in old people, principally women, and 
usually from a very slight degree of indirect violence. Probably the main cause of the fracture 
taking" place in old people is in consequence of the degenerative changes which the bone has 
undergone. Merkel believes that it is mainly due to the absorption of the calcar femorale. 
These fractures are occasionally impacted. As a rule, they unite by fibrous tissue, and frequently 
no union takes place, and the surfaces of the fracture become smooth and eburnated. The 
lack of reparative power in intracapsular fracture is due to lack of apposition of the fragments and 
diminution in the amount of blood sent to the smaller fragment. The head of the bone receives 
blood from the neck through the reflected portions of the capsule and through the ligamentum 
teres. A fracture cuts off the supply by the neck and by the reflected portions of the capsule. 

Fractures at the junction of the rieck with the great trochanter are usually termed extracap- 
sular, but this designation is also incorrect, as the fracture is partly within the capsule, owing 
to its attachment in front to the anterior intertrochanteric line, which is situated below die line 
of fracture. These fractures are produced by direct violence to the great trochanter, as from a 
blow or fall laterally on the hip. From the rnanner in which the accident is caused, the neck of 
the bone is driven 'into the trochanter, where it may remain impacted or the trochanter may 
split up into two or more fragments, and thus no fixation takes place. 

Fractures of the great trochanter may be either "oblique fracture through the trochanter 
major, without implicating the neck of the bone" (Astley Cooper), or separation of the great 
trochanter. Most of the "recorded cases of this latter injury occurred in young persons, and 
were probably cases of separation of the epiphysis of the great trochanter. Sepai-ation of_ the 
epiphysis of the head of the femur has been said to occur, but has probably never been verified 
by postmortem examination. 



230 SPECIAL ANATOMY OF THE SKELETON 

Fracture of the shaft may occur at any part, but the most usual situation is at or near the 
centre of the bone. They may be caused by direct or indirect violence or by muscular action. 
Fractures of the upper third of the shaft are almost always the result of indirect violence, while 
those of the lower third are the result, for the most part, of direct violence. In the middle third 
fractures occur from both forms of injury in about equal proportions. Fractures of the shaft 
are generally oblique, but they may be transverse, longitudinal, or spiral. The transverse frac- 
ture occurs most frequently in children. The fractures of the lower end of the femur include 
transverse fracture above the condyles, the most common; and this may be complicated by a 
vertical fracture between the condyles, constituting the T-shaped fracture. In these cases the 
popliteal artery is in danger of being wounded. Oblique fracture, separating either the internal 
or external condyle, and a longitudinal incomplete fracture between the condyles, may also take 
place. 

The femur and also the bones of the leg are frequently the seat of acute osteomyelitis in young 
children. This is no doubt due to their greater exposure to injury, which is often the exciting 
cause of this disease. Tumors not infrequently are found growing from the femur, the most 
common forms being sarcoma, which may grow either from the periosteum or from the medullary 
tissue within the interior of the bone; and exostosis, which is commonly found originating in 
the neighborhood of the epiphyseal cartilage of the lower end. 

Genu varum is a form of how-leg in which the tibia and femur are curved outward, the knees 
being widely separated. Both extremities are usually affected. In early life the disease is due 
to rhachitis. In elderly people it may be due to arthritis deformans. Genu valgum (knock-knee) 
is a condition in which the knees are close together, the feet are wide apart, and the internal 
lateral ligament of the knee-joint is stretched. It is due to excessive growth of the inner con- 
dyle of the femur, the shaft of the femur curving inward. It may be due to rhachitis, attitude of 
an occupation, or flat-foot, and one or both knees may be affected. 



THE LEG. 

The skeleton of the leg consists of three bones — the patella, a large sesamoid 
bone, placed in front of the knee; the tibia; and the fibula. 



The Patella, or Kneecap (Fig. 184). 

The patella is a flat, triangular bone, situated at the anterior part of the knee- 
joint. It is usually regarded as a sesamoid bone, developed in the tendon of 
the Quadriceps extensor. It serves to protect the front of the joint, and in- 
creases the leverage of the 
Quadriceps extensor by making 
it act at a greater angle. It 
presents an anterior and a pos- 
terior surface, three borders, 
and an apex. 

Surfaces. — The anterior sur- 
face is convex, perforated by 
small apertures, for the passage 
of nutrient vessels, and marked 
by numerous rough, longitudi- 

FlQ. 184.— Right patella. A. Anterior surface. B. Posterior yisI StrisB This SUrfaCC is COV- 
surface. i • 'i 

ered, ni the recent state, by an 
expansion from the tendon of the Quadriceps extensor, which is continuous 
below with the superficial fibres of the ligamentum patellae. It is separated 
from the integument by a bursa. 

The posterior surface presents a smooth, oval-shaped, articular surface {fades 
articidaris), covered with hyaline cartilage in the recent state, and divided into two 
facets by a vertical ridge, which descends from the superior border toward the 
inferior angle of the bone. The ridge corresponds to the groove on the trochlear 




THJiJ TIBIA, OB. SHIN BONE 231 

surface of the femur, and the two facets to the articular surfaces of the two con- 
dyles; the outer facet, for articulation with the outer condyle, being broader and 
deeper. This character serves to indicate the side to which the bone belongs. 
Below the articular surface is a rough, convex, nonarticular depression, the lower 
half of which gives attachment to the ligamentum patellae, the upper half being 
separated from the head of the tibia by adipose tissue. 

Borders. — The superior border (basis patellae) is thick, and sloped from Ijehind, 
downward and forward; it gives attachment to that portion of the Quadriceps 
extensor which is derived from the Rectus femoris and Crureus muscles. 

The lateral borders are thinner, converging below. They give attachment 
to that portion of the Quadriceps extensor derived from the external and internal 
Vasti muscles. 

The apex (ape.r patellae) is pointed, and gives attachment to the ligamentum 
patellae. 

Structure. — This bone resembles a sesamoid bone (1) in being developed in a tendon; (2) in 
its centre of ossification presenting a knotty or tuberculated outline; (3) in its structure being 
composed mainly of dense cancellous tissue. It consists of a nearly uniform, dense cancellous 
tissue covered by a thin compact lamina. The cancelli immediately beneath the anterior surface 
are arranged parallel with it. In the rest of the bone they radiate from the posterior articular 
surface toward the other parts of the bone. 

Development. — From a single centre, which makes its appearance in the second or third, but 
may not ajjpear until the sixth year. More rarely, the bone is developed by two centres, placed 
side by side. Ossification is completed about the age of puberty. 

Articulations. — With the two condyles of the femur. 

Attachment of Muscles. — To four — the Rectus, Crureus, Vastus internus, and Va.stus 
externus. These muscles, joined at their insertion, constitute the Quadriceps extensor cruris. 

Surface Form. — The external surface of the patella can be seen and felt in front of the knee. 
In the extended position of the limb the internal border is a little more prominent than the 
outer, and if the Quadriceps extensor is relaxed the bone can be moved from side to side and 
appears to be loosely fixed. If the joint is flexed, the patella recedes into the hollow between the 
condyles of the femur and the upper end of the tibia, and becomes firmly fixed against the femur. 

Applied Anatomy. — The main surgical interest about the patella is in connection with frac- 
tures, which are of common occurrence. They may be produced by muscular action; that is 
to say, by violent contraction of the Quadriceps extensor while the limb is in a position of semi- 
flexion, so that the bone is snapped across the condyles; or by direct violence, such as falls on 
the knee. Most fractures are due to muscular action; in fact, the patella is more often broken 
by muscular action than is any other bone. In fractures by muscular action the line of fracture 
is transverse. In fractures by direct force the line of fracture may be oblique, longitudinal, 
stellate, or the bone variously comminuted. The principal interest in these cases attaches to 
their treatment. Owing to the wide separation of the fragments, and the difficulty there is in 
maintaining them in apposition, union takes place by fibrous tissue, and this may subsequently 
stretch, producing wide separation of the fragments and permanent lameness. Various plans, 
including opening the joint and suturing the fragments, have been advocated for overcoming 
this difficulty. In many cases a portion of fascia or capsule gets between the fragments. In 
such a condition operation is necessary. 

In the larger number of cases of fracture of the patella the l>nee-joint is involved, the car- 
tilage which covers its posterior surface being torn, the s3'novial membrane lacerated, the lateral 
fibrous expansions ruptured, and the patellar bm-sa torn open. In cases of fracture from direct 
violence, however, this need not necessarily happen, the lesion may involve only the superficial 
part of the bone; and, as Morris has pointed out, it is an anatomical possibility, in complete 
fracture, if the lesion involve only the lower and nonarticular part of the bone, for it to take 
place without injury to the synovial membrane. 



The Tibia, or Shin Bone (Figs. 185, 186). 

The tibia is situated at the front and inner side of the leg, and, excepting the 
femur, is the longest and largest bone in the skeleton. It is prismoid in form, 
expanded above, where it enters into the knee-joint, more slightly enlarged below. 



232 SPECIAL ANATOMY OF THE SKELETON 

Capsular ligament 



Sti/loid -y, 




External malleohts. 



Capsular ligament 



Fig. 1S5. — Bones of the right leg. .interior surface. Fig. 186.— Bones of the right leg. Posterior surface. 



THE TIBIA, OR SHIN BONE 



233 



In the male its direction is vertical and parallel with the bone of the opposite 
side; but in the female it has a slightly oblique direction downward and outward, 
to compensate for the oblique direction of the femur inward. It presents for 
examination a shaft and two extremities. 

The Proximal or Upper Extremity.— The upper extremity, or head, is 
large, and expanded on each side into two lateral eminences, the internal and 
external tuberosities (coiidijlus medialis and condylus lateralis). Superiorly, each 
tuberosity presents a smooth, concave surface {fades articularis superior), which 
articulates with a condyle of the femur. The internal articular surface is oval in 
shape and concave from side to side; the external one is circular, concave from side 
to side, but slightly convex from before backward, especially at its posterior 
part, where it is prolonged on to the posterior surface for a short distance; the 
central portions of these surfaces articulate with the condyles, while the peripheral 
portions are overlaid by the semilunar cartilages of the knee. Between the two 
articular surfaces, and nearer the posterior than the anterior aspect of the bone, 
is an eminence, the spine of the tibia (eminentia intercondijloidea); surmounted 
by a prominent tubercle on each side (the tuherculum intercond.yloideum mediale 
and the tuherculum intercondyloideuni laterale), on to the lateral aspect of which 



External semilunar 
cartilage. 



Po-iterior crucial 
llqatntnt 



External semilunar 
cartilage. 




Anterior crucial 
ligament. 



Internal scmiluruir 
cartilage. 



Internal semilunar 
cartilage. 



Fig. 187. — Upper surfaces of right tibia, showing attachment of crucial ligaments 
cartilages have been partly cut away. 



nd semilunar cartilages. The 



the facets just described are prolonged; in front and behind the spinous process 
is a rough depression (fossa intercondyloidea anterior and the fossa intercondy- 
loidea posterior) for the attachment of the anterior and posterior crucial ligaments 
and the semilunar fibrocartilages (Fig. 187). 

The anterior surfaces of the tuberosities are continuous with one another, form- 
ing a single large surface, which is somewhat flattened; it is triangular, broad 
above, and perforated by large vascular foramina; narrow below, where it ter- 
minates in a prominent oblong elevation of large size, the tubercle of the tibia 
{tuberositas tibiae); the lower half of this tubercle is rough, for the attachment of 
the ligamentura patellae; the upper half presents a smooth facet supporting, in 
the recent state, a bursa which separates the ligament from the bone. Poste- 
riorly the tuberosities are separated from each other by a shallow depression, 
the popliteal notch {incisura poplitea), which gives attachment to part of the pos- 
terior crucial ligament and part of the posterior ligament of the knee-joint. The 
inner tuberosity presents posteriorly a deep transverse groove, for the insertion 
of one of the fasciculi of the tendon of the Semimembranosus (Fig. 266) . Its lateral 
surface is convex, rough, and prominent, and gives attachment to the internal 
lateral ligament. The outer tuberosity presents posteriorly a flat articular facet 
{fades articidaris fibidaris) , nearly circular in form, directed downward, backward. 



234 SPECIAL ANATOMY OF THE SKELETON 

and outward, for articulation with the fibula. Its lateral surface is convex and 
rough, more prominent in front than the internal, and presents a prominent 
rough eminence, situated on a level with the upper border of the tubercle of the 
tibia at the junction of its anterior and outer surfaces, for the attachment of the 
iliotibial band. Just below this the Extensor longus digitorum arises, and a slip 
from the Biceps femoris cruris is attached. x 

Shaft of the Tibia (corpus tibiae). — The shaft of the tibia is of a triangular 
prismoid form, broad above, gradually decreasing in size to its most slender part, 
the commencement of its lower fourth; it then enlarges again toward its lower 
extremity. It presents for examination three borders and three surfaces. 

The anterior border, the most prominent, is called the crest of the tibia (crista 
anterior) ; it commences above at the tubercle, and terminates below at the anterior 
margin of the inner malleolus. This border is very prominent in the upper 
two-thirds of its extent, smooth and rounded below. It presents a very sinuous 
course, being usually curved outward above and inward below; it gives attachment 
to the deep fascia of the leg. 

The internal border (margo medialis) is smooth and rounded above and below, 
but more prominent in the centre; it commences at the back part of the inner tuber- 
osity, and terminates at the posterior border of the internal malleolus; its upper 
part gives attachment to the internal lateral ligament of the knee to the extent 
of about two inches, and to some fibres of the Popliteus muscle, and its middle 
third to some fibres of origin of the Soleus and Flexor, longus digitorum muscles.. 

The external border (crista interossea), or interosseous ridge, is thin and prominent, 
especially its central part, and gives attachment to the interosseous membrane; 
it commences above in front of the fibular articular facet, and bifurcates below, 
to form the boundaries of a triangular rough surface, for the attachilient of the 
interosseous ligament connecting the tibia and fibula. 

The internal surface (fades medialis) is smooth, convex, and broader above than 
below; its upper third, directed forward and inward, is covered by the aponeurosis 
derived from the tendon of the Sartorius, and by the tendons of the Gracilis and 
Semitendinosus, all of which are inserted nearly as far forward as the anterior 
border; in the rest of its extent it is subcutaneous. 

The external surface (fades lateralis) is narrower than the internal; its upper 
two-thirds presents a shallow groove for the origin of the Tibialis anticus muscle; 
its lower third is smooth, convex, curves gradually forward to the anterior aspect 
of the bone, and is covered from within outward by the tendons of the following 
muscles: Tibialis anticus. Extensor proprius hallucis. Extensor longus digitorum. 

The posterior surface (fades posterior) (Fig. 186) presents, at its upper part, a 
prominent ridge, the oblique line of the tibia (l.inea poplitea), which extends from 
the back part of the articular facet for the fibula obliquely downward, to the in- 
ternal border, at the junction of its upper and middle thirds. It marks the lower 
limit for the insertion of the Popliteus muscle, and serves for the attachment of 
the popliteal fascia and part of the Soleus, Flexor longus digitorum, and Tibialis 
posticus muscles; the triangular concave surface, above and to the inner side of 
this line, gives attachment to the Popliteus muscle. The middle third of the 
posterior surface is divided by a vertical ridge into two lateral halves; the ridge 
is well marked at its commencement at the oblique line, but becomes gradually 
indistinct below; the inner and broader half gives origin to the Flexor longus 
digitorum, the outer and narrower to part of the Tibialis posticus. The remaining 
part of the bone presents a smooth surface covered by the Tibialis posticus. 
Flexor longus digitorum, and Flexor longus hallucis muscles. Immediately 
below the oblique line is the nutrient foramen, which is large and directed obliquely 
downward. It is the opening of the nutrient canal, which is directed toward the 
ankle. 



THE TIBIA, OB SHIN BONE 



235 



Upper rxtmnity. 



The Distal or Lower Extremity.— The lower extremity, much smaller than 
the upper, presents five surfaces; it is prolonged downward, on its inner side, 
to a strong process, tiie internal malleolus (malleolus medialis). 

The inferior surface (Jacicn cniiciilaris inferior) of the bone is cjuadrilateral, 
and smooth for articulation with the astragalus. This surface is concave from 
before backward, and broader in front than behind. It is traversed from 
before backward by a slight elevation, separating two lateral depressions. It is 
narrow internally, where the articular surface becomes continuous with that on 
the inner malleolus. 

The anterior surface of the lower extremity is smooth and rounded above, and 
covered by the tendons of the Extensor muscles of the toes; its lower margin 
presents a rough transverse depression, for the attachment of the anterior ligament 
of the ankle-joint. 

The posterior surface presents a superficial groove directed obliquely downward 
and inward, continuous with a similar groove on the posterior surface of the as- 
tragalus, and serving for the passage of the tendon of the Flexor longus hallucis. 

The external surface presents a triangular rough depression for the attachment 
of the interior interosseous ligament, connecting it with the fibula; the lower part 
of this depression, the iiicisura fibularis, is smooth, covered with cartilage in the 
recent state, and articulates with the fibula. This surface is bounded by two 
prominent borders, continuous above with the interosseous ridge; they afford 
attachment to the anterior inferior and posterior inferior tibiofibular ligaments. 

The internal surface of the lower extremity is prolonged downward to form a 
strong pyramidal process, flattened from without inward — the internal malleolus 
(malleolus medialis). The inner surface of this process is convex and subcu- 
taneous; its outer surface is smooth and 
slightly concave, and articulates with the 
astragalus; its anterior border is rough, 
for the attachment of the anterior fibres 
of the internal lateral or deltoid ligament; 
its posterior border presents a broad and 
deep groove (sulcus malleolar is), directed 
obliquely downward and inward, which 
is occasionally double; this groove trans- 
mits the tendons of the Tibialis posticus 
and Flexor longus digitorum muscles. 
The apex of the internal malleolus is 
marked by a rough depression behind, 
for the attachment of the internal lateral 
ligaments of the ankle-joint. 

Structure.— Like that of the other long bones. 
At the junction of the middle and lower third, 
where the bone is smallest, the wall of the shaft 
is thicker than in other parts, in order to com- 
pensate for the smallness of the calibre of the 
bone. 

Development. — From three centres (Fig. 
1 88), one for the shaft and one for each extrem- 
ity. Ossification commences in the centre of the 
shaft about the seventh week, and gradually ex- 
tends toward either extremity. The centre for the 
upper epiphysis appears before or shortly after 

birth; it is flattened in form, and has a thin, tongue-shaped process in front which forms the 
tubercle. That for the lower epiphysis appears in the second year. The lower epiphysis 
joins the shaft at about the eighteenth, and the upper one about the twentieth year. T\yo 
additional centres occasionally exist — one for the tongue-shaped process of the upper epiphysis, 
which forms the tubercle, and one for the inner malleolus. 



Appenrs shorily 
after birth. 



Appears at Snd_ 
year. 




Joins shaft ahout 
20th year. 



_Joins shaft about 
ISlh year. 



236 SPECIAL ANATOMY OF THE SKELETON 

Articulations. — With three bones — the femur, fibula, and astragalus. 

Attachment of Muscles. — To twelve: To the inner tuberosity, the Semimembranosus; to the 
outer tuberosity, the Tibialis anticus and Extensor longus digitorum and Biceps femoris, to the 
shaft, its internal surface, the Sartorius, Gracilis, and Semitendinosus; to its external surface, 
the Tibialis anticus; to its posterior surface, the Popliteus, Soleus, Flexor longus digitorum, and 
Tibialis posticus; to the tubercle, the ligamentum patellae, by which the Quadriceps extensor 
muscle is inserted into the tibia. In addition to these muscles, the Tensor fasciae femoris is 
inserted indirectly into the tibia, through the iliotibial band, and the Peroneus longus occasionally 
derives a few fibres of origin from the outer tuberosity. 

Surface Form. — A considerable portion of the tibia is subcutaneous and easily felt. At the 
upper extremity the tuberosities are to be recognized just below the knee. The internal one is 
broad and smooth, and merges into the subcutaneous surface of the shaft below. The external 
one is narrower and more prominent, and on it, about midway between the apex of the patella 
and the head of the fibula, may be felt a prominent tubercle for the insertion of the iliotibial 
band. In front of the upper end of the bone, between the tuberosities, is the tubercle of the 
tibia, forming an oval eminence which is continuous below with the anterior border or crest 
of the bone. This border can be felt, forming the prominence of the shin, in the upper two- 
thirds of its extent as a sharp and sinuous ridge, curved outward above and inward below. In 
the lower third of the leg the border disappears, and the bone is concealed by the tendons of the 
muscles on the front of the leg. Internal to the anterior border is to be felt the broad internal 
surface of the tibia, slightly encroached upon by the muscles in front and behind. It com- 
mences above at the wide expanded inner tuberosity, and terminates below at the internal malle- 
olus. The internal malleolus is a broad prominence situated on a higher level and somewhat 
farther forward than the external malleolus. It overhangs the inner border of the arch of the 
foot. Its anterior border is nearly straight; its posterior border presents a sharp edge which 
forms the inner margin of the groove for the tendon of the Tibialis posticus muscle. 

The Fibula, or Calf Bone (Figs. 185, 186). 

The fibula is situated at the outer side of the leg. It is the smaller of the two 
bones, and, in proportion to its length, the most slender of all the long bones; it 
is placed on the outer side of the tibia, with which it is connected above and below. 
Its upper extremity is small, placed toward the back of the head of the tibia and 
below the level of the knee-joint, and excluded»4i'om its formation; the lower 
extremity inclines a little forward, so as to be on a plane anterior to that of the 
upper end, projects below the tibia, and forms the outer ankle. It presents 
for examination a shaft and two extremities. 

The Proximal or Upper Extremity. — The upper extremity, or head (capitu- 
limi fibulae), is of an irregular quadrate form, presenting above a flattened articular 
facet, directed upward, forward, and inward, for articulation with a corresponding 
facet on the external tuberosity of the tibia. On the outer side is a thick and 
rough prominence, continued behind into a pointed eminence, the styloid process 
of the fibula (apex capituli fibulae), which projects upward from the posterior 
part of the head. The prominence gives attachment to the tendon of the Biceps 
femoris muscle and to the long external lateral ligament of the knee, the ligament 
dividing the tendon into two parts. The apex of the styloid process gives at- 
tachment to the short external lateral ligament. The remaining part of the 
circumference of the head is rough, for the attachment of muscles and ligaments. 
It presents in front a tubercle for the origin of the upper and anterior part of the 
Peroneus longus, and the adjacent surface gives attachment to the anterior 
superior tibiofibular ligament; and behind, another tubercle for the attachment 
of the posterior superior tibiofibular ligament and the upper fibres of origin of 
the Soleus muscle. 

The Shaft (corpus fibulae).^ — The shaft presents four borders — the antero- 
external, the antero-internal, the postero-external, and the postero-internal; and 
four surfaces — anterior, posterior, internal, and external. 

• Authorities differ as to the best description of the borders and surfaces of the shaft of the fibula. The editor has 
followed the scheme in general use at the present time. A more appropriate plan might be afforded by the consid- 
eration of three surfaces: extensor, peroneal, and flexor, the last being subdivided by the oblique ridge. — Editor. 



THE FIBULA, OR CALF BONE 237 

The antero-external border (crista anterior) commences above in front of the 
head, runs vertically downward to a little below the middle of the bone, and then, 
curving somewhat outward, bifurcates so as to embrace the triangular subcutane- 
ous surface immediately above the outer surface of the external malleolus. This 
border gives attachment to an intermuscular septum, which separates the Extensor 
muscles on the anterior surface of the leg from the Peroneus longus and brevis 
muscles on the outer surface. 

The antero-intemal border (crista iuterossea), or interosseous ridge, is situated 
close to the inner side of the preceding, and runs nearly parallel with it in the upper 
third of its extent, but diverges from it so as to include a broader space in the lower 
two-thirds. It commences above, just beneath the head of the bone (sometimes 
it is quite indistinct for about an inch below the head), and terminates below at 
the apex of a rough triangular surface immediately above the articular facet of 
the external malleolus. It serves for the attachment of the interosseous membrane, 
which separates the Extensor muscles in front from the Flexor muscles behind. 

The postero-extemal border (crista lateralis) is prominent; it commences above 
at the base of the styloid process, and terminates below in the posterior border 
of the outer malleolus. It is directed outward, above, backward in the middle 
of its course, backward and a little inward below, and gives attachment to an 
aponeurosis which separates the Peronei muscles on the outer surface of the shaft 
from the Flexor muscles on its posterior surface. 

The postero-intemal border (crista medialis) sometimes called the oblique line, 
commences above at the inner side of the head, and terminates by becoming 
continuous with the interosseous ridge at the lower fourth of the bone. It is 
well marked and prominent at the upper and middle parts of the bone. It gives 
attachment to an aponeurosis which separates the Tibialis posticus from the 
Soleus above and the Flexor longus hallucis below. 

The anterior siirface {Jacies anterior) is the interval between the antero-external 
and antero-internal borders. It is extremely narrow and flat in the upper third 
of its extent, broader and grooved longitudinally in its lower third; it serves for 
the origin of three muscles, the Extensor longus digitorum, Peroneus tertius, 
and Extensor proprius hallucis. 

The external surface Q'acies lateralis) is the space between the antero-external 
and postero-external borders. It is much broader than the preceding, and often 
deeply grooved, is directed outward in the upper two-thirds of its course, backward 
in the lower third, where it is continuous with the posterior border of the external 
malleolus. This surface is completely occupied by the Peroneus longus and brevis 
muscles. 

The internal surface (fades medialis) is the interval included between the antero- 
internal and the postero-internal borders. It is directed inward, and is grooved 
for the origin of the Tibialis posticus muscle. 

The posterior surface (Jacies posterior) is the space included between the postero- 
external and the postero-internal borders; it is continuous below with the rough 
triangular surface above the articular facet of the outer malleolus; it is directed 
backward above, backward and inward at its middle, directly inward below. 
Its upper third is rough, for the origin of the Soleus muscle; its lower part presents 
a triangular rough surface, connected to the tibia by a strong interosseous ligament, 
and between these two points the entire surface is covered by the fibres of origin 
of the Flexor longus hallucis muscle. At about the middle of this surface is the 
nutrient foramen. It opens into the nutrient canal, which is directed downward. 

The Distal or Lower Extremity.— The lower extremity, or external malleolus 
(malleolus lateralis), is of a pyramidal form, somewhat flattened from without in- 
ward, and is longer, and descends lower than the internal malleolus. Its external 
surface is convex, subcutaneous, and continuous with the triangular (also sub- 



238 



SPECIAL ANATOMY OF THE SKELETON 



cutaneous) surface on the outer side of the shaft. The internal surface presents 
in front a smooth triangular facet {fades artlcularis malleoli), broader above than 
below, and convex from above downward, which articulates with a corresponding 
surface on the outer side of the astragalus. Behind and beneath the articular 
surface is a rough depression which gives attachment to the posterior fasciculus 
of the external lateral ligament of the ankle. The anterior border is thick and 
rough, and marked below by a depression for the attachment of the anterior 
fasciculus of the external lateral ligament. The posterior border is broad and 
marked by a shallow groove (sulcus malleolaris), for the passage of the tendons 
of the Peroneus longus and brevis muscles. The ai:iex is rounded, and gives 
'attachment to the middle fasciculus of the external lateral ligament. 



Interosseous 

I "fi border 




Upper extremity. 



Appears atout ^ 
4th year. ^ 



. Unites about 
' S5th year. 



For post, fascic. of 
extl. lateral ligt. 



Appeals at JSM Unites about 
Sndyea, ~\W\ -Othyear. 

I.oirer erfremify. 



-Lower extremity of right fibula. 
Internal aspect. 



In order to distinguish ttie side to wliich the bone belongs, hold it with the lower extremit}^ 
downward and the broad groove for the Peronei tendons backward — i. e., toward the holder; 
the triangular subcutaneous surface will then be directed to the side to which the bone belongs. 

Development. — From three centres (Fig. 190) — one for the shaft and one for each extremity. 
Ossification commences in the shaft about the eighth week of fetal life, a little later than in the 
tibia, and extends gradually toward the extremities. At birth both ends are cartilaginous. Ossifi- 
cation commences in the lower end in the second year, and in the upper one about the fourth 
year. The lower epiphysis, the first in which ossification commences, becomes united to the 
shaft about the twentieth year; the upper epiphysis joins about the twenty-fifth year. Ossifi- 
cation appearing first in the lower epiphysis is contrary to the rule which prevails with regard 
to the commencement of ossification in epiphyses — viz., that epiphysis toward which the nutrient 
artery is directed commences to ossify last; but it follows the rule which prevails with regard to 
the union of epiphyses, by uniting first. 

Articulations. — With two bones: the tibia and astragalus. 

Attachment of Muscles.— To nine: To the head, the Biceps femoris, Soleus, and Peroneus 
longus; to the shaft, its anterior surface, the Extensor longus digitorum, Peroneus tertius, and 
Extensor proprius hallucis; to the internal surface, the Tibialis posticus; to the posterior surface, 
the Soleus and Flexor longus hallucis, to the external surface, the Peroneus longus and brevis. 

Surface Form. — The only parts of the fibula which may be fe't are the head and the lower 
part of the externa! surface of the shaft and the external malleolus. The head may be seen 



THE FOOT 239 

and felt behind and to the outer side of the outer tuberosity of the tibia. It presents a small, 
prominent triangular eminence slightly above the level of the tubercle of the tibia. The exter- 
nal malleolus presents a narrow elongated prominence, situated on a plane posterior to the 
internal malleolus and reaching to a lower level. From it may be traced the lower third or 
half of the external surface of the shaft of the bone in the interval between the Peroneus tertius 
in front and the other two Peronei tendons behind. 

Applied Anatomy. — In fractures of the bones of the ley both bones are usually fractured, but 
either bone may be broken separately, the fibula more frequently than the tibia. Fracture of 
both bones may be caused either by direct or indirect violence. When it occurs from indirect 
force the fracture in the tibia is usually at the junction of the middle and lower third of the bone. 
Many causes conduce to render this the weakest part of the bone. The fracture of the fibula 
is usually at rather a higher level. These fractures present great variety, both as regards their 
direction and condition. They may be oblique, transverse, longitudinal, or spiral. When 
oblique, they are usually the result of indirect violence, and the direction of the fracture is from 
behind, downward, forward, and inward in many cases, but may be downward and outward 
or downward and backward. When transverse, the fracture is often at the upper part of the 
bone, and is the result of direct violence. The spiral fracture usually commences as a vertical 
fissure, involving the ankle-joint, and is associated with fracture of the fibula higher up. It is 
the result of torsion, from twisting of the body while the foot is fixed. 

Fractures of the tiliia alone are almost always the result of direct violence, except where the 
malleolus is broken off by twists of the foot. Fractures of the fibula alone may arise from indi- 
rect or direct force, those of the lower end being usually the result of the former, and those higher 
up being caused by a direct blow on the part. 

The tibia and fibula, like the femur, are frequently the seat of acute osteomyelitis. Tuhemdoiis 
abscess is more frequently met with in the cancellous tissue of the head and lower end of the 
tibia than in any other bone of the body. The abscess is of small size, very chronic, and prob- 
ably the result of tuberculous osteitis in the highly vascular growing tissue at the end of the shaft 
near the epiphyseal cartilage in the young subject. Such an abscess in bone is called Brodie's 
abscess. 

The tibia is the bone which is most frequently and most extensively distorted in rhachitis. It 
gives way at the junction of the middle and lower third, its weakest part, and presents a curve 
forward and outward. Boto-leg is due to outward curvature of the femur, tibia, and fibula, 
the bend being about the junction of the shafts and lower extremities. 



THE FOOT (Figs. 191, 192). 

The skeleton of the foot consists of three divisions — the tarsus, metatarsus, and 
phalanges. 

The Tarsus (os.m tarsi). — The hones of the tarsus are seven in number — 
viz., tlie calcaneus, or os calcis, astragalus, cuboid, scaphoid, internal, middle, and 
external cvmeiform. 

The Calcaneus (os calcis) (Fig. 194). — The heel bone is the largest and strongest 
of the tarsal bones. It is irregularly cuboidal in form, having its long axis directed 
forward and outv\ard. It is situated at the lower and back part of the foot, 
serving to transmit the weight of the body to the ground, and forming a strong 
lever for the muscles of the calf. It presents for examination six surfaces — 
superior, inferior, external, internal, anterior, and posterior. 

The superior surface is formed, behind, by the upper aspect of that part of the 
OS calcis which projects backward to form the heel. It varies in length in different 
individuals; is convex from side to side, concave from before backward, and cor- 
responds above to a mass of adipose substance placed in front of the tendo Achillis. 
In the middle of the superior surface are two (sometimes three) articular facets, 
separated by a broad shallow groove (sulcus calcanei), which is directed obliquely 
forward and outward, and is rough for the attachment of the interosseous ligament 
connecting the astragalus and os calcis. When the calcaneus is in contact with 
the astragalus this groove is converted into a canal (sinus tarsi). Of the articular 
surfaces, the posterior articular siu-face (fades articularis posterior) is th^ larger, and 
is situated on the body of the bone; it is of an oblong form, wider behind than in 



240 



SPECIAL ANA TOMY OF THE SKELETON 




Fig. 191. — Bones of the right foot. Dorsal surface. 



THE FOOT 



241 



AOOESSOniU&. 



,rLExcR snevis hallucis. 




Fig. 192. — Bones of the right foot. Plantar surface. 
16 



242 



SPECIAL ANA T03IY OF THE SKELETON 



front, and convex; it articulates with the posterior articular area of the astragalus. 
The anterior articular stirf ace is usually divided into two facets, the anterior of which 
(fades articularis anterior) supports the head of the astragalus. The more pos- 
teriorly situated facet (fades articularis calcanea media) articulates with the middle 
facet on the under surface of the astragalus. The anterior articular surface is 
supported on a projecting process of bone, called the lesser process of the cal- 
caneus (sustentaculum tali); it is oblong, concave longitudinally, and sometimes 
subdivided into two parts, which differ in size and shape. IMore anteriorly is 

seen the upper surface of the greater 
process of the calcaneus, marked bv a 
rough depression for the attachment 
of numerous ligaments, and a tubercle 
for the origin of the Extensor brevis 
digitorum muscle. 

The inferior surface is narrow, 
rough, uneven, wider behind than in 
front, and convex from side to side; 
it is bounded posteriorly by two 
tubercles separated by a rough de- 
pression; the external tubercle (pro- 
cessus lateralis tuberis calcanei), small, 
prominent, and rounded, gives origin 
to part of the Abductor minimi 
digiti; the internal tubercle (processus 
medialis tuberis calcanei), broader and 
larger, for the support of the heel, 
gives origin, by its prominent inner 
margin, to the Abductor hallucis, and 
in front to the Flexor brevis digitorum 
muscle and plantar fascia; the de- 
pression between the tubercles gives 
origin to the Abductor minimi digiti. 
The rough surface in front of the 
tubercles gives attachment to the long 
plantar ligament and origin to the 
outer head of the Flexor accessorius 
muscle; while to a prominent tubercle 
nearer the anterior part of this sur- 
face, as well as to a transverse groove 
in front of it, is attached the short 
plantar ligament. 
The external surface is broad, flat, and almost subcutaneous; it presents near 
its centre a tubercle, for the attachment of the middle fasciculus of the exter- 
nal lateral ligament. At its upper and anterior part this surface gives attach- 
ment to the external calcaneo-astragaloid ligament; and in front of the tubercle 
it presents a narrow surface marked by two oblique grooves; separated by an 
elevated ridge which varies much in size in different bones, it is named the peroneal 
spine {processus trochlear is), and gives attachment to a fibrous process from the 
external annular ligament. The superior groo-ve transmits the tendon of the 
Peroneus brevis; the inferior groove the tendon of the Peroneus longus. 

The internal surface is deeply concave; it is directed obliquely downward and 
forward, and serves for the transmission of the plantar vessels and nerves into the 
sole of the foot; it affords origin to part of the Flexor accessorius muscle. At 
its upper and fore part it presents an eminence of bone, the sustentaculum tali, 




Fig. 193, — Schematic representation of the articula- 
tions of the tarsus. Occasional articulations shown hy 



THE FOOT 



243 



which projects horizontally inward, and to it a slip of the tendon of the Tibialis 
posticus is attached. This process is concave above, and supports the anterior 
articular surface of the astragalus; below, it is grooved for the tendon of the Flexor 
longus hallucis. Its free margin is rough, for the attachment of part of the 
internal lateral ligament of the ankle-joint. 

The anterior surface {fades articularis cuhoidea), of a somewhat triangular 
form, articulates with the cuboid. It is concave from above downward and out- 
ward, and convex in the opposite direction. Its inner border gives attachment 
to the inferior calcaneoscaphoid ligament. 



Groove for Peroneus bre. 

A. 




Feroneal tubercle 

Groove for Feroneus longus 



tendo AchiUia 



External- tubercle 



B 



For posterim- facet of astragal:is 
For middle facet of astragalus 

For ntitei tor facet of astragalus 




Internal tubercle 
Groove for Flexor longus hallucis 

Sustentaculum tali 

Groove for interosseous ligament 

Fig. 194. — The left calcaneus. A. Postero-external view. B. Antero-internal view. 

The posterior surface is rough, prominent, convex, and wider below than above. 
The posterior extremity is the projection of the heel. It is called the tuberosity 
(tuber calcanei). Its lower part is rough, for the attachment of the tendo Achillis 
and the tendon of the Plantaris muscle; its upper part is smooth, and is covered 
.by a bursa which separates the tendons from the bone. 



244 



SPECIAL ANA TOMY OF THE SKELETON 



Articulations. — With two bones — the astragalus and cuboid. 

Attachment of Muscles. — To eight, part of the TibiaHs posticus, the tendo Achilhs, Plan- 
taris, Abductor hallucis, Abductor minimi digiti, Flexor brevis digitorum, Flexor accessorius, 
and Extensor brevis digitorum. 



For scaphoid Neck A Sup. surface, for tibia 

' For inferior tibiofibular 

ligament 




For ext. malleolus 



For int. malleoUu 



Sup. surface, fur tihia 



Groove for Flexor longus \ . ^ 

hallucis 



For inferior calcaneo 
navicular ligament 



Middle calcaneal 
facet 



Posterior calcaneal 
facet 



Groove for Flex, 
long, hallucis 




For scaphoid 



'For scaphoid 
j{ ~~~^~i^ZW -interior calcaneal facet 



Groove for interosseous 
ligaynent 



Fig. 195. — The left astragalus. A. Supero-external 



C. Inferior view. 



The Astragalus, or Ankle Bone {talus) (Fig. 195).— The astragaliLS is the second 
largest of the tarsal bones. It occupies the middle and upper part of the tarsus, 
supporting the tibia above, articulating with the malleoli on either side, resting 
below upon the calcaneus, and joined in front to the scaphoid. This bone may 



THE FOOT 245 

be easily recognized by its large rounded head, by the broad articular facet on its 
upper convex surface, and by the two articular facets separated by a deep groove 
on its under concave surface. It presents six surfaces for examination. 

The superior surface presents, behind, a broad smooth trochlear surface {trochlea 
tali) for articulation with the tibia. The trochlea is broader in front than behind, 
convex from before backward, slightly concave from side to side; in front of it is the 
upper surface of the neck of the astragalus, rough for the attachment of ligaments. 

The inferior surface presents two articular areas separated by a deep groove 
{svlcits tali). The groove runs obliquely forward and outward, becoming gradu- 
ally broader and deeper in front; it corresponds with a similar groove upon the 
upper surface of the calcaneus, and forms, when articulated with that bone, a 
canal, filled up in the recent state by the calcaneo-astragaloid ligament. Of 
the two articular areas, the posterior (fades articularis calcanea posterior) is the 
larger, of an oblong form, and deeply concave from side to side ; it rests on the 
posterior articular surface of the os calcis; the anterior articular area is shorter 
and narrower, of an elongated oval form, convex longitudinally, and most often 
subdivided into two facets by an elevated ridge; of these, the posterior (fades 
articularis calcanea media) articulates with the hinder portion of the anterior 
articular surfaces of the calcaneus; the anterior (fades articularis calcanea anterior) 
rests upon the anterior portion of the anterior articular surface of the calcaneus 
just mentioned. 

The internal surface presents at its upper part a pear-shaped articular facet (fades 
malleolaris medialis) for the inner malleolus, continuous above with the trochlear 
surface; below the articular surface is a rough depression, for the attachment 
of the deep portion of the internal lateral ligajnent. 

The external surface presents a large triangular facet (fades malleolaris lateralis), 
concave from above downward for articulation with the external malleolus; 
it is continuous above with the trochlear surface; and in front of it is a rough 
depression for the attachment of the anterior fasciculus of the external lateral 
ligament of the ankle-joint. 

The anterior surface (fades articularis navicularis) forms the head of the astrag- 
alus, is convex and rounded, smooth, of an oval form, and directed obliquely 
inward and downward; it articulates with the scaphoid. On its under and inner 
surface is a small facet, continuous in front with the articular surface of the head, 
and behind with the anterior articular area for the calcaneus. This rests on the 
inferior calcaneoscaphoid ligament, being separated from it by the syno\ial mem- 
brane. The head is attached to the rest of the bone by a constricted portion, the 
neck of the astragalus (collum tali). 

The posterior surface is traversed by a groove (sidcus m. flexoris hallucis longi), 
which runs obliquely downward and inward, and transmits the tendon of the 
Flexor longus hallucis, external to which is the prominent external tubercle (pro- 
cessus posterior tali), to which the posterior fasciculus of the external lateral 
ligament is attached. This tubercle is sometimes separated from the rest of the 
astragalus, and is then known as the os trigonum. 

To ascertain to which foot the bone belongs, hold it with the broad articular surface upward, 
and the rounded head forward; the lateral triangular articular surface for the external malleolus 
will then point to the side to which the bone belongs. 

Articulations. — With four bones — tibia, fibula, calcaneus, and scaphoid. 

The Cuboid (os cuboideum) (Fig. 196). — The cuboid is placed on the outer 
side of the foot, in front of the calcaneus, and behind the fourth and fifth meta- 
tarsal bones. It is of a pyramidal shape, its base being directed inward, its apex 
outward. It may be distinguished from the other tarsal bones by the existence 



246 SPECIAL ANATOMV OF THE SKELETON 

of a deep groove on its under surface, for the tendon of the Peroneus longus muscle. 
It presents for examination six surfaces, three articular and three nonarticular. 
The nonarticular surfaces are the dorsal, plantar, and external. The dorsal 
surface, directed upward and outward, is rough, for the attachment of numerous 
ligaments. The plantar surface presents in front a deep groove, the peroneal 
groove (sulcus m. peroiiei loncji), which runs obliquely from without, forward and 
inward; it lodges the tendon of the Peroneus longus, and is bounded behind by 
a prominent ridge, to which is attached the long calcaneocuboid ligament. The 
ridge terminates externally in an eminence (tuberositas ossi-s cuboidei), the surface 
of which presents a convex facet, for articulation with the sesamoid bone of the 
tendon contained in the groove. The surface of bone behind the groove is rough, 
for the attachment of the short plantar ligament, a few fibres of origin of the 
Flexor brevis hallucis, and a fasciculus from the tendon of the Tibialis posticus. 
The external surface, the smallest and narrowest of the three, presents a deep 
notch formed by the commencement of the peroneal groove. 



For ext. cuneiform For 4tk -metatarsal 



Occasional facet 
for scaphoid 




Fui 5th 
tatarsal 




Groovefor Tubeiositij Foi ralcaneni 
Peroneus 
longus B 

Fig. 196. — The left cuboid. .-1. .\ntero-internaI view. B. Postero-external view. 

The articular surfaces are the posterior, anterior, and internal. The posterior 
surface is smooth, triangular, and concavo-convex, for articulation with the 
anterior surface of the calcaneus. The anterior surface, of smaller size, but also 
irregularly triangular, is divided by a vertical ridge into two facets : the inner one, 
quadrilateral in form, articulates with the fourth metatarsal bone; the outer one, 
larger and more triangular, articulates with the fifth metatarsal. The internal 
surface is broad, rough, irregularly quadrilateral, presenting at its middle and 
upper part a smooth oval facet, for articulation with the external cuneiform bone; 
and behind this (occasionally) a smaller facet, for articulation with the scaphoid; 
it is rough in the rest of its extent, for the attachment of strong interosseous liga- 
ments. 

To ascertain to which foot the bone belongs, hold it so that its under surface, marked by the 
peroneal groove, looks downward, and the large concavo-convex articular surface backward 
toward the holder: the narrow nonarticular surface, marked by the Commencement of the 
peroneal groove, will point to the side to which the bone belongs. 

Articulations. — With foiir bones — the calcaneus, external cuneiform, and the fourth and fifth 
metatarsal bones; occasionally with the scaphoid. 

Attachment of Muscles. — Part of the Flexor brevis hallucis and a slip from the tendon of 
the Tibialis posticus. 

Scaphoid or Navicular Bone (os naviculare pedis) (Fig. 197). — The scaphoid is 
situated at the inner side of the tarsus, between the astragalus behind and the 
three cuneiform bones in front. It may be distinguished by its form, being con- 
cave behind, convex and subdivided into three facets in front. 

The anterior surface, of an oblong form, is convex from side to side, and sub- 
divided by two ridges into three facets, for articulation with the three cuneiform 
bones. The posterior surface is oval, concave, broader externally than internally. 



THE FOOT 



247 



and articulates with the rounded head of the astragalus. The dorsal surface is 
convex from side to side, and rough for the attachment of ligaments. The plantar 
is irregular, and also rough for the attachment of ligaments. The internal surface 
presents a rounded tubercular eminence, the tuberosity {tuberositas ossis navicu- 
laris), the lower part of which projects, and gives attachment to part of the tendon 
of the Tibialis posticus. The external surface is rough and irregular, for the 
attachment of ligamentous fibres, and occasionally presents a small facet for 
articulation with the cuboid bone. 



For viid. cuneiforin 



For int. cuneifoi m 





Fig. 197 —The left scaphoid 



For astragalus Tubercle 



eternal view. B. Postero-internal view. 



For Znd For 

For 1st metatarsal metatarsal mid-cuneiform 



To ascertain to which foot the bone belongs, hold it" with the concave articular surface back- 
ward, and the convex dorsal surface upward; the external surface — i. e., the surface opposite 
the tubercle — will point to the side to which the bone belongs. 

Articulations. — With four bones — astragalus and three cuneiform; occasionally also with 
the cuboid. 

Attachment of Muscles. — Part of the Tibialis posticus. 

Cuneiform or Wedge Bones. — The cuneiform bones have received their name 
from their wedge-like shape. They form, with the cuboid, the distal row of 
the tarsus, being placed between the scaphoid behind, the three innermost meta- 
tarsal bones in front, and the 
cuboid externally. They are 
called the first, second, and 
third, counting from the inner 
to the outer side of the foot, 
and, from their position, in- 
ternal, middle, and external. 

Internal or First Cuneiform 
{OS cuneiforms primum) (Fig. 
198). — The internal cuneiform 
is the largest of the three. It 
is situated at the inner side of- 
the foot, between the scaphoid 
behind and the base of the first 
metatarsal in front. It may be 
distinguished from the other 

two by its large size, and by its not presenting such a distinct wedge-like form. 
Without the others it may be known by the large, kidney-shaped anterior articu- 
lating surface and by the prominence on the inferior or plantar surface for the 
attachment of the Tibialis posticus. It presents for examination six surfaces. 

The internal surface is subcutaneous, and forms part of the inner border of the 
foot; it is broad, quadrilateral, and presents at its anterior inferior angle a smooth 
oval facet, into which the tendon of the Tibialis anticus is partially inserted; 
in the rest of its extent it is rough, for the attachment of ligaments. The external 





For tendon of 
Tibialis anticus 



For scapticrid 



Antero-internal view. 



248 SPECIAL ANATOMY OF THE SKELETON 

surface is concave, presenting, along its superior and posterior borders, a narrow, 
reversed, I>-shaped surface, for articulation with the middle cuaeiform behind 
and second metatarsal bone in front; in the rest of its extent it is rough, for the 
attachment of ligaments, and part of the tendon of the Peroneus longus. The 
anterior surface, kidney-shaped, much larger than the posterior, articulates with 
the metatarsal bone of the great toe. The posterior surface is triangular, concave, 
and articulates with the innermost and largest of the three facets on the anterior 
surface of the scaphoid. The plantar surface is rough, and presents a prominent 
tuberosity at its back part for the attachment of part of the tendon of the Tibialis 
posticus. It also gives attachment in front to part of the tendon of the Tibialis 
anticus. The dorsal surface is the narrow-pointed end of the wedge, which is 
directed upward and outward; it is rough for the attachment of ligaments. 

To ascertain to which side the bone belongs, hold it so that its dorsal narrow edge looks 
upward, and the long, kidney-shaped, articular surface forward; the external surface, marked 
by its vertical and horizontal articular facets, will point to the side to which it belongs. 

Articulations. — With four bones: scaphoid, middle cuneiform, first and second metatarsal 
bones. 

Attachment of Muscles. — To three — the Tibialis anticus and posticus, and Peroneus longus. 

Middle or Second Cuneiform (os cuneiforme secundum) (Fig. 199). — The middle 
cuneiform, the smallest of the three, is of very regular wedge-like form, the broad 
extremity being placed upward, the narrow end downward. It is situated between 

the other two bones of the same 
For int. cuneiform p^^ scaphoid "ame, and articulates with the 

scaphoid behind and the second 
metatarsal in front. It is smaller 
than the external cuneiform bone, 
from which it may be further dis- 
tinguished by the L-shaped artic- 
ular facet, which runs around the 
„ „ , \ , • T. . .t^„ upper and back part of its inner 

.For 2nd metatarsal For ext cuneiform ff r 

surface. 

Fig. 199. — The left middle cuneiform. A. Antero-mtern.il rr^, . . , 

view. B. Postero-externai view. i he anterior surface, triangular 

in form and narrower than the 
posterior, articulates with the base of the second metatarsal bone. The posterior 
surface, also triangular, articulates with the scaphoid. The internal surface 
presents an L-shaped articular facet, running along the superior and posterior 
borders, for articulation with the internal cuneiform, and is rough in the rest of its 
extent, for the attachment of ligaments. The external surface presents posteriorly a 
smooth facet for articulation with the external cuneiform bone. The dorsal 
surface forms the base of the wedge; it is quadrilateral, broader behind than in 
front, and rough for the attachment of ligaments. The plantar surface, pointed 
and tubercular, is also rough for ligamentous attachment and for the insertion 
of a slip from the tendon of the Tibialis posticus. 

To ascertain to which foot the bone belongs, hold its superior or dorsal surface upward, the 
broadest edge being toward the holder; the smooth facet (limited to the posterior border) will 
then point to the side to which it belongs. 

Articulations. — With four bones — scaphoid, internal and external cuneiform, and second 
metatarsal bone. 

Attachment of Muscles. — A slip from the tendon of the Tibialis posticus is attached to 
this bone. 

External or Third Cuneiform (os cuneiforme terfium) (Fig. 200). — The external 
cuneiform, intermediate in size between the two preceding, is of a very regular 
wedge-like form, the broad extremity being placed upward, the narrow end down- 





TH1<J FOOT 



249 



ward. It occupies the centre of the front row of the tarsus, between the middle 
cuneiform internally, the cuboid externally, the scaphoid behind, and the third 
metatarsal in front. It is distinguished from the internal cuneiform bone by its 
more regular wedge-like shape and by the absence of the kidney-shaped articular 
surface; from the middle cuneiform, by the absence of the L-shaped facet, and 
by the two articular facets which are present on both its inner and outer surfaces. 
It has six surfaces for examination. 

The anterior surface, triangular in form, articulates with the third metatarsal 
bone. The posterior surface articulates with the most external facet of the scaphoid, 
and is rough below for the attachment of ligamentous fibres. The internal 
surface presents two articular facets, separated by a rough depression; the anterior 
one, sometimes divided into two, articulates with the outer side of the base of 
the second metatarsal bone; the posterior one skirts the posterior border and articu- 
lates with the middle cuneiform; the rough depression between the two gives 
attachment to an interosseous ligament. The external surface also presents two 
articular facets, separated by a rough nonarticular surface; the anterior facet, 
situated at the superior angle of the bone, is small, and articulates with the inner 
side of the base of the fourth metatarsal ; the posterior and larger one articulates 
with the cuboid; the rough, nonarticular surface serves for the attachment of 



For scaphoid For tniddle-cuneiforin 




For Uh 
metatarsal' For cuhoid 



Fig. 200. — The left external cuneiform. A. Postero-internal 




Antero-external view. 



an interosseous ligament. The three facets for articulation with the three meta- 
tarsal bones are continuous with one another, and covered by a prolongation of 
the same cartilage; the facets for articulation with the middle cuneiform and 
scaphoid are also continuous, but that for articulation with the cuboid is usually 
separate. The dorsal surface is of an oblong square form, its posterior external 
angle being prolonged backward. The plantar surface is an obtuse rounded 
margin, and serves for the attachment of ligaments and a part of the tendon of 
the Tibialis posticus, and for part of the fibres of origin of the Flexor brevis hallucis. 

To ascertain to which side the bone belongs, hold it with the broad dorsal surface upward, 
the prolonged edge backward; the separate articular facet for the cuboid will point to the proper 
side. 

Articulations. — With dx bones — the scaphoid, middle cuneiform, cuboid, and second, third, 
and fourth metatarsal bones. 

Attachment of Muscles. — To two— ]>3,vt of the Tibialis posticus, and Flexor brevis hallucis. 

The number of tarsal bones may be reduced owing to congenital ankylosis which may occur 
between the os calcis and cuboid, the os calcis and scaphoid, the os calcis and astragalus, or the 
astragalus and scaphoid. 



The Metatarsal Bones (ossa metatarsalia). — The metatarsal bones are five 
in number, and are numbered one to five, in accordance with their position from 
within outward; they are long bones, and present for examination a shaft and two 
extremities. 



250 



SPECIAL ANATOMY OF THE SKELETON 



Common Characters. — The shaft (corpus) is prismoid in form, tapers gradually 
from the tarsal to the phalangeal extremity, and is slightly curved longitudinally, 
so as to be concave below, slightly convex above. On the plantar surface of the 

shaft of each bone is a nutrient 
foramen corresponding to the 
nutrient foramen in each meta- 
carpal bone. The proximal 
extremity, or base (basis), is 
wedge-shaped, articulating by 
its terminal surface with the 
tarsal bones, and by its lateral 
surfaces with the contiguous 
metatarsal bones, its dorsal and 
plantar surfaces being rough for 
the attachment of ligaments. 
The distal extremity, or head 
(capitvlvvi) , presents a terminal 
rounded articular surface, oblong 
from above downward, and ex- 
tending farther backward below 
than above. Its sides are flat- 
tened and present a depression, 
surmounted by a tubercle, for 
ligamentous attachment. Its 
under surface is grooved in the middle line for the passage of the Flexor tendon, 
and marked on each side by an articular eminence continuous with the terminal 
articular surface. 




Occasional Jati t joi 
second metatarsal. 



For internal cuneiform, 

Fig. 201. — The first metatarsal. (Left.) 




Occii'^iimnl 

I /ai et for first „ , , 

I metatarsal. ^"'^ external 

For middle cuneiform. cimeijorm. 




\ For second metatarsal. 
For middle cuneiform. 



For fourth 
metatarsal. 



Fig. 202. — The second metatar.sal. (Left.) 



Fig. 203. — The third metatarsal. (Left.) 



Peculiar Characters. — The metatarsal bone of the great toe (os metatarsale I) 
(Fig. 201) is remarkable for its great thickness, but is the shortest of all the 
metatarsal bones. The shaft is strong and of well-marked prismoid form. The 



THE FOOT 251 

proximal extremity presents, as a rule, no lateral articular facet, but occasionally 
on the outer side there is an oval facet by which it articulates with the second 
metatarsal bones. Its proximal articular surface is of large size and kidney 
shaped; it corresponds to the distal extremity of the internal cuneiform; its cir- 
cumference is grooved, for the tarsometatarsal ligaments, and internally gives 
attachment to part of the tendon of the Tibialis anticus muscle; its inferior angle 
presents a rough oval prominence, the tuberosity {tuberositas ossis metatarsalis I), 
for the insertion of the tendon of the Peroneus longus. The head is of large size; 
on its plantar surface are two grooved facets, over which glide sesamoid bones; 
the facets are separated by a smooth elevated ridge. 

This bone is known by the single kidney-shaped articular surface on its base, the deeply 
grooved appearance of the plantar surface of its head, and its great thickness relatively to its 
length. When it is placed in its natural position, the concave border of the kidney-shaped 
articular surface on its l)ase points to the side to which the bone belongs. 

Attachment of Muscles. — To three — part of the Tibialis anticus, the Peroneus longus, and 
the First dorsal interosseous. 

The second metatarsal (os metaiarsale II) (Fig. 202) is the longest and largest 
of the remaining metatarsal bones, being prolonged backward into the recess 
formed between the three cuneiform bones. Its tarsal extremity is broad above, 
narrow and rough below. It presents four articular surfaces — one behind, of 
a triangular form, for articulation with the middle cuneiform; one at the upper 
part of its internal lateral surface, for articulation with the internal cuneiform; 
and two on its external lateral surface — an upper and a lower, separated by 
a rough nonarticular interval. Each of these articular surfaces is divided by a 
vertical ridge into two facets, thus making four facets; the two anterior of these 
articulate with the third metatarsal; the two posterior (sometimes continuous) 
with the external cuneiform. In addition to these articular surfaces there is 
occasionally a fifth when this bone articulates with the first metatarsal bone. 
It is oval in shape, and is situated on the inner side of the shaft near the base. 

The facets on the tarsal extremity of the second metatarsal bone serve at once to distinguish it 
from the rest, and to indicate the foot to which it belongs; there being one facet at the upper 
angle of the internal surface, and two facets, each subdivided into two parts, on the external 
surface, pointing to the side to which the bone belongs. The fact that the two posterior subdi- 
visions of these external facets sometimes run into one should not be forgotten. 

Attachment of Muscles.— To /o((r— the Adductor obliquus hallucis, First and Second 
dorsal interossei, and a slip from the tendon of the Tibialis posticus; occasionally also a slip 
from the Peroneus longus. 

The third metatarsal (os metatarsale III) (Fig. 203) articulates proximally, by 
means of a triangular smooth surface, with the external cuneiform; on its inner 
side, by two facets, with the second metatarsal; and on its outer side, by a single 
facet, with the fourth metatarsal. The latter facet is of circular form and situated 
at the upper angle of the base. 

The third metatarsal is known by possessing at its tarsal end two undivided facets on the inner 
side, and a single facet on the outer. This distinguishes it from the second metatarsal, in which 
the two facets, found on one side of its tarsal end, are each subdivided into two. The single facet 
(when the bone is put in its natural position) is on the side to which the bone belongs. 

Attachment of Muscles.— To five — Adductor obliquus hallucis, Second and Third dorsal 
and First plantar interossei, and a slip from the tendon of the Tibialis posticus. 

The fourth metatarsal {os metatarsale IV) (Fig. 204) is smaller in size than the 
preceding; its tarsal extremity presents a terminal quadrilateral surface, for articu- 
lation with the cuboid; a smooth facet on the inner side, divided by a ridge into 
an anterior portion for articulation with the third metatarsal, and a posterior 



252 



SPECIAL ANATOMY OF THE SKELETON 



portion for articulation with the external cuneiform; on the outer side a single 
facet, for articulation with the fifth metatarsal. 

The fourth metatarsal is known by its having a single facet on either side of the tarsal extrem- 
xty, that on the inner side being divided into two parts. If this subdivision be not recognizable, 
the fact that its tarsal end is bent somewhat outward will indicate the side to which it belongs. 

Attachment of Muscles.^To five — Adductor obliquus hallucis. Third and Fourth dorsal, 
and Second plantar interossei, and a slip from the tendon of the Tibialis posticus. 

The fifth metatarsal bone, or the metatarsal bone of the little toe {os metatarsale V) 
(Fig. 205), is recognized by the tubercle (tuberositas ossis metatarsalis V) on the 
outer side of its base. It articulates behind, by a triangular surface cut obliquely 
from without inward, with the cuboid, and internally with the fourth metatarsal. 




For cuboid* 
For ext. cuneiform. 

Fig. 204.— The fourth metatarsal. (Left.) 



Tuberosity. 



For fourth \ 
vietatarsal. 

For cuboid. 

Fig. 205. — The fifth metatarsal. (Left.) 



The projection on the outer side of this bone at its tarsal end at once distinguishes it from 
the others, and points to the side to which it belongs. 

Attachment of Muscles. — To si.v — the Peroneus brevis, Peroneus tertius, Flexor brevis 
minimi digiti, Adductor transversus hallucis, Fourth dorsal, and Third plantar interossei. 

Articulations. — Each bone articulates with the tarsal bones by one extremity (proximal), and 
by the other (distal) extremity with the first row of phalanges. The number of tarsal bones 
with which each metatarsal articulates is one for, the first, three for the second, one for the third, 
tw'o for the fourth, and one for the fifth. 



The Phalanges of the Foot (Phalanges Digitorum Pedis). 

The phalanges of the foot, both in number and general arrangement, resemble 
those in the hand-; there being two in the great toe and three in each of the other 
toes. The nutritive foramina correspond to those in the phalanges of the hand. 

The first or proximal phalanx (phalanx prima) resembles closely the corre- 
sponding bone of the hand. The shaft also is compressed from side to side, 
convex above, concave below. The proximal extremity is concave; and the distal 
extremity presents a trochlear surface, for articulation with the second phalanx. 



THE FOOT 



253 



The second phalanx (phalanx secwida) is remarkably small and short, but 
rather broader than the first phalanx. 

The ungual or distal phalanx (phalanx terfia) in form resembles the bone of the 
corresponding finger, but is smaller, flattened from above downward, presenting 
a broad base for articulation with the second phalanx, and an expanded extremity 
for the support of the nail and end of the toe. 



y s I s. 



> Appears 10th year ; 

imites after puberty. 



Tarsus. 

One centre for each toiie, 

except calcaneus 



Two centres for each totie 
One for shaft, 
One for digital cMtreit 
except 1st. 



Phalanges 
Two centres for each hone : 
One for shaft. 
One for proximal 
extremity. 




3d year. 
Unite ISth-SO year. 

Appears 7th week. 



Appeal s 9th week 

Unite 18th 20th yeai 
Appears Sth-Sth year. 

Appears M^i year. 
Unite 17-18th year. | 
Appears Snd-4th month. 



Appears 6th-7lh year. 



Unite 17th-18th year. ■, 

Appears Snd-4th month.~^-~J fi \ / 

Appears 6th year.^ 3 ^^ 

Unite 17th-18th year.AW S 
Appears 10th week.—vj'^ 

Fig. 206. — Plan of the development of the foot. 



Articulation. — The first row, with the metatarsal bones behind and second phalanges in 
front; the second row of the four outer toes, with the first and third phalanges; of the great toe, 
with the fir.st plialanx; tlie third row of the four outer toes, with the second phalanges. 

Attachment of Muscles. — To the first phalanges: Great toe, five muscles— innermost tendon 
of E.xteiisor l)ievis diijitorum, Abductor hallucis. Adductor obliquus hallucis. Flexor brevis 
hallucis, Adductor transversus hallucis. Second toe, three muscles — First and Second dorsal 
interosseous and First lumbrical. Third toe, three muscles — Third dorsal and First plantar inter- 
osseous and Second lumbrical. Fourth toe, three muscles — Fourth dorsal and Second plantar 
interosseous and Third lumbrical. Fifth toe, four muscles — Flexor brevis minimi digiti, Abduc- 
tor minimi digiti, and Third plantar interosseous, and Fourth lumbrical. Second phalanges: 
Great toe — Extensor longus huUucis, Flexor longus hallucis. Other toes — Flexor brevis digitorum, 
one slip of the common tendon of the Extensor longus and brevis digitorum.' Third phalanges: 
Two slips from the common tendon of the Extensor longus and Extensor brevis digitorum, and 
the Flexor longus digitorum. 



Except the second phalanx of the fifth toe, which 



no slip from the Extensor brevis digitorum. 



254 SPECIAL ANATOMY OF THE SKELETON 



Development of the Foot (Fig. 206). 

The tarsal bones are each developed from a single centre, excepting the calcaneus, which has 
an epiphysis for its posterior extremity. The centres make tlieir appearance in the following 
order: calcaneus, at the sixth month of fetal life; astragalus, about the seventh month; cuboid, 
at the ninth month; external cuneiform, during the first year; internal cuneiform, in the third 
year; middle cuneiform and scaphoid, in the fourth year. The epiphysis for the posterior 
tuberosity of the calcaneus appears at the tenth year, and unites with the rest of the bone soon 
after puberty. When this part remains as a separate bone, it is called the oa trigonum. 

The metatarsal bones are each developed from two centres — one for the shaft and one for the 
digital extremity in the four outer metatarsal; one for the shaft and one for the base in the metatar- 
sal bone of the great toe.^ Ossification commences in the centre of the shaft about the ninth week, 
and extends toward either extremity. The centre in the proximal end of the first metatarsal 
bone appears about the third year, the centre in the distal end of the other bones between the fifth 
and eighth years; they unite with the shaft between the eighteenth and twentieth years. 

The phalanges are de\'eloped from two centres for each bone — one for the shaft and one for 
the proximal extremity. The centre for the shaft appears about the tenth week, that for the 
epiphysis between the fourth and tenth years ; they join the shaft about the eighteenth year. 



Construction of the Foot as a Whole (Figs. 207, 208). 

The foot is constructed on the same principles as the hand, but modified to 
form a firm Ijasis of support for the rest of the body when in the erect position. 
It is more solidly constructed, and its component parts are less movable on each 
other than in the hand. This is especially the case with the great toe, M'hich has 
to assist in supporting the body, and is therefore constructed with greater solidity; 
it lies parallel with the other toes, and has a very limited degree of mobility, 
whereas the thumb, which is occupied in numerous and varied movements, is 
constructed in such a manner as to permit of great mobility. Its metacarpal bone 
is directed away from the others, so as to form an acute angle with the second, 
and it enjoys a considerable range of motion at its articulation with the carpus. 
The foot is placed at right angles to the leg — a position which is almost peculiar 
to man, and has relation to the erect position which he maintains. In order to 
allow of its supporting the weight of the whole body in this position with the 
least expenditure of material, it is constructed in the form of an arch. This 
antero-posterior or longitudinal arch is made up of two unequal limbs. The 
hinder one, which is made up of the calcaneus and the posterior part of the astrag- 
alus, is about half the length of the anterior limb, and measures about three 
inches. The anterior limb consists of the rest of the tarsal and the metatarsal 
bones, and measures about seven inches. It may be said to consist of two parts, 
an inner segment made up of the head of the astragalus, the scaphoid, the three 
cuneiform, and the three inner metatarsal bones; and an outer segment composed 
of the calcaneus, the cuboid, and the two outer metatarsal bones. The summit of 
the arch is at the superior articular surface of the astragalus; and its two extremi- 
ties — that is to say, the two piers on which the arch rests in standing^are the 
internal tubercle on the under surface of the calcaneus posteriorly, and the heads 
of the metatarsal bones anteriorly. The weakest part of the arch is the joint 
between the astragalus and scaphoid; and here it is more liable to yield in those 
who are overweighted, and in those in whom the ligaments which complete and 
preserve the arch are' relaxed. This weak point in the arch is braced on its con- 
cave surface by the inferior calcaneoscaphoid ligament, which is more elastic 
than most other ligaments, and thus allows the arch to yield from jars or shocks 
applied to the anterior portion of the foot and quickly restores it to its pristine 

' As was noted in the first metacarpal bone, so in the first metatarsal, there is often to be observed a tendency 
to the formation of a second epiphysis in the distal extremity. 



CONSTRUCTION OF THE FOOT AS A WHOLE 



255 



condition. This ligament is supported internally by blending with the deltoid 
ligament, and inferiorly by the tendon of the Tibialis posticus muscle, which is 
spread out into a fan-shaped insertion, and prevents undue tension of the liga- 
ment or such an amount of stretching as would permanently elongate it. 

In addition to this longitudinal arch the foot presents a transverse arch, at the 
anterior part of the tarsus and hinder part of the metatarsus. This, however, can 
scarcely be described as a true arch, but presents more the character of a half- 
dome. The inner border of the central portion of the longitudinal arch is elevated 




Fig. 207. — Skeleton of the foot, internal border. (Poirier and Charpy.) 

from the ground, and from this point the bones arch over to the outer border, 
which is in contact with the ground, and, assisted by the longitudinal arch, pro- 
duce a sort of rounded niche on the inner side of the foot, which gives the appear- 
ance of a transverse as well as a longitudinal arch. 

The line of the foot, from the point of the heel to the toes, is not quite straight, 
but is directed a little outward, so that the inner border is a little convex and the 
outer border concave. This disposition of the bones becomes more marked when 
the longitudinal arch of the foot is lost, as in the condition known under the name 
of "flat-foot." 



OLE CUNEIFORM 



ST METATARSAL 




Fig. 20S. — Skeleton of the foot, external border. (Poirier and Charpy.) 



Surface Form. — On the dorsum of the foot the individual bones are not to be distinguished 
■with the e.x'ception of the head of the astragalus, which forms a rounded projection in front of 
the ankle-joint when the foot is forcibly extended. The whole surface forms a smooth convex 
outline, the summit of which is the ridge formed by the head of the astragalus, the scaphoid, 
the middle cuneiform, and the second metatarsal bones; from this it gradually inclines outward 
and more rapidly inward. On the inner side of the foot, the internal tubercle of the calcaneus 
and the ridge separating the inner from the posterior surface of the bone may be felt most pos- 
teriorly. In front of this, and below the internal malleolus, may be felt the projection of the 
sustentaculum tali. Passing forward is the well-marked tuberosity of the scaphoid bone, situ- 
ated about an inch or an inch and a quarter in front of the internal malleolus. Further toward 
the front, the ridge formed by the base of the first metatarsal bone can be obscurely felt, and 
from this the shaft of the bone can be traced to the expanded head articulating with the base 



256 SPECIAL ANATOMY OF THE SKELETON 

of the first phalanx of the great toe. Immediately beneath the base of this phalanx, the internal 
sesamoid bone is to be felt. Lastly, the expanded ends of the bones forming the last joint of 
the great toe are to be felt. On the outer side of the foot the most posterior bony point is the 
external tubercle of the calcaneus, with the ridge separating the posterior from the outer surface 
of the bone. In front of this the greater part of the external siu^face of the calcaneus is subcu- 
taneous; on it, below and in front of the external malleolus, may be felt the peroneal spine when 
this is present. Farther forward, the base of the fifth metatarsal bone forms a prominent and 
well-defined landmark, and in front of this the shaft of the bone, with its expanded head, and 
the base of the first phalanx may be defined. The sole of the foot is almost entirely covered 
by soft parts, so that but few bony parts are to be made out, and these somewhat obscurely. 
The hinder part of the under surface of the calcaneus and the heads of the metatarsal bones, 
with the exception of the first, which is concealed by the sesamoid bones, may be recognized. 

Applied Anatomy. — Considering the injuries to which the foot is subjected, it is surpris- 
ing how seldom the tarsal bones are fractured. This is no doubt due to the fact that the tarsus 
is composed of a number of bones, articulated by a considerable extent of surface and joined 
together by very strong ligaments, which serve to mitigate the intensity of violence applied to this 
part of the body. When fracture does occur, these bones, being composed for the most part 
of a soft cancellous structure, covered only by a thin shell of compact tissue, are often extensively 
comminuted, especially as most of the fractures are produced by direct violence. As the bones 
have only a very scanty amount of soft parts over them, fractures are very often compound, and 
amputation is frequently necessary. 



CALCANEUS 





of Chopart's amputation. Fig. 210. — Line of Lisfranc's amputation, 

(Poirier.) (Poirier.) 

When fracture occurs in the anterior group of tarsal bones, it is almost invariably the result 
of direct violence, but fractures of the posterior group, that is, of the calcaneus and astragalus, 
are most frequently produced by falls from a height on to the feet; though fracture of the cal- 
caneus may be caused by direct violence or by muscular action. The posterior part of the bone, 
that is, the part behind flie articular surfaces, is almost always the seat of the fracture, though 
some few cases of fracture of the sustentaculum tali and of vertical fracture between the two 
articulating facets have been recorded. The neck of the astragalus, being the weakest part of 
the bone, is most frequently fractured, though fractures may occur in any part and almost in 
any direction, either associated or not with fracture of other bones. 

In cases of club-foot, especially in congenital cases, the bones of the tarsus become altered 
in shape and size, and displaced from their proper positions. This is especially the case in 
congenital equinovarus, in which the astragalus, particularly about the head, becomes twisted and 
atrophied, and a similar condition may be present in the other bones, more especially the 
scaphoid. The tarsal bones are peculiarly liable to become the seat of tuberculous caries, and this 
condition may arise after comparatively trivial injuries. There are several reasons to account 
for this. They are composed of a delicate cancellated structure, surrounded by intricate synovial 
membranes. They are situated at the farthest point from the central organ of the circulation 
and exposed to vicissitudes of temperature; and, moreover, on their dorsal surface are thinly 
clad with soft parts which have but a scanty blood-supply. And finally, after slight injuries, 
they are not maintained in a condition of rest to the same extent as structures suffering from 
similar injuries in some other parts of the body. Caries of the calcaneus or astragalus may 
remain limited to the one bone for a long period, but when one of the other bones is affected, 
the remainder frequently become involved, in consequence of the disease spreading through 
the large and complicated synovial membrane which is more or less common to these bones. 

Amputation of the whole or a part of the foot is frequently required either for injury or disease. 
The principal amputations are as follows: (1) Syme's amputation at the ankle-joint by a heel- 
flap, with the removal of the malleoli and a thin slice from the lower end of the tibia. (2) 
Pirogoff's amputation: removal of the whole of the tarsal bones, except the posterior part of the 



SESAMOID BONES 



257 



calcaneus. A thin slice is sawed from the tibia and fibula, including the two malleoli. The sawed 
surface of the calcaneus is then turned up and united to the similar surface of the tibia. (.3) 
Subastragaloid amputation: removal of the foot below the astragalus through the joint between 
it and the calcaneus. 

The bones of the tarsus occasionally recjuire removal individually. This is especially the 
case with the astragalus and calcaneus for disease limited to the one bone, or again the 
astragalus may require excision in cases of subastragaloid dislocation. In cases of in\'eterate 
talipes the head of the astragalus and greater process of the calcaneus is often removed, some- 
times the scaphoid is also taken out. Finally, Mikulicz and Watson have devised operations for 
the removal of more extensive portions of the tarsus. Mikulicz's operation consists in the re- 
moval of the calcaneus and astragalus, along with the articular surfaces of the tibia and fibula, 
and also of the scaphoid and cuboid. The remaining portion of the tarsus is then brought 
into contact with the sawed surfaces of the tibia and fibula, and fixed there. The result is a 
position of the shortened foot resembling talipes ecjiiinus. Watson's operation is adapted to 
those cases where the disease is confined to the anterior tarsal bones. By two lateral incisions 
he saws through the bases of the metatarsal bones in front and opens up the joints between the 
scaphoid and astragalus, and the cuboid and calcaneus, and removes the intervening bones. 

Fractures of the metatarsal bones and phalanges are nearly always due to direct violence, and 
in many cases the injury is the result of severe crushing accidents, necessitating amputation. 
The metatarsal bones, and especially the metatarsal bone of the great toe are frequently dis- 
eased, either in tuberculous subjects or in perforating ulcer of the foot. 



Sesamoid Bones (Ossa Sesamoidea) (Figs. 211, 212). 

These are small rounded masses, cartilaginous in early life, osseous in the adult, 
which are developed in those tendons which exert a great amount of pressure upon 





Fig. 211 —Sesamoid bones of the hand. (Poirier 
and Charpy.) 

the parts over which they glide. It is said that they are more commonly found in 
the male than in the female, and in persons of an active muscular habit than in 
those who are weak and debilitated. They are invested throughout their whole 
surface by the fibrous tissue of the tendon in which they are found, excepting upon 
that side which lies in contact with the part over which they play, where they 
present a Iree articular facet. They may be divided into two kinds — those 



258 SPECIAL ANATOMY OF THE SKELETON 

which glide over the articular surfaces of the joints, and those which play over 
the cartilaginous facets found on the surfaces of certain bones. 

The sesamoid bones of the joints in the upper extremity are two on the palmar 
surface of the metacarpophalangeal joint in the thumb, developed in the tendons 
of the Flexor brevis poUicis; one on the palmar surface of the interphalangeal 
joint of the thumb; occasionally one or two opposite the metacarpophalangeal 
articulations of the fore and little fingers; and, still more rarely, one opposite the 
same joints of the third and fourth fingers. In the lower extremity, the patella, 
which is developed in the tendon of the Quadriceps extensor; two small sesamoid 
bones, found in the tendons of the Flexor brevis hallucis, opposite the metatarso- 
phalangeal joint of the great toe; one sometimes over the interphalangeal joint 
of the great toe; and occasionally one in the metatarsophalangeal joint of the 
second toe, the little toe, and, still more rarely, the third and fourth toes. 

Those found in the tendons which glide over certain bones occupy the following 
situations: One sometimes found in the tendon of the Biceps brachii, opposite the 
tuberosity of the radius; one in the tendon of the Peroneus longus, where it glides 
through the groove in the cuboid bone; one appears late in life in the tendon of 
the Tibialis anticus, opposite the smooth facet of the internal cuneiform bone; 
one is found in the tendon of the Tibialis posticus, opposite the inner side of the 
head of the astragalus; one in the outer head of the Gastrocnemius, behind the 
outer condyle of the femur; and one in the conjoined tendon of the Psoas and 
Iliacus, where it glides over the os pubis. Sesamoid bones are found occasionally 
in the tendon of the Gluteus maximus, as it passes over the great trochanter, and 
in the tendons which wind around the inner and outer malleolL 



THE AETICULATIONS, OE JOINTS. 



THE various bones of which the skeleton consists are connected at different 
parts of their surfaces, and such connections are designated hv the 
name of joints, or articulations. Certain joints are immovable, as all those between 
the cranial bones excepting the temporomandibular joint. In an immovable joint 
the adjacent margins of the Ijones are applied in close contact, a thin layer of 
fibrous membrane, the sutural ligament, or, as at the base of the skull, in certain 
situations, a thin layer of cartilage, being interposed. Where slight movement is 
required, combined with great strength, the osseous surfaces are united by tough 
and elastic fibrocartilages, as in the joints between the vertebral bodies and 
in the interpubic articulation; but in the movable joints the bones forming the 
articulation are generally expanded for greater convenience of mutual connection, 
covered by hyaline cartilage, held together by strong bands or capsules of fibrous 
tissue called ligaments, and partially lined by a membrane, the synovial membrane, 
which transudes a fluid to lubricate the various parts of which the joint is formed; 
so that the structures which enter into the formation of a joint are bone, hyaline 
cartilage, fibrocartilage, ligament, and synovial membrane 

Bone. — Bone constitutes the fundamental element of all the joints In the 
long bones the extremities are the parts which form the articulations; they' are 
generally somewhat enlarged, and consist of spongy, cancellous tissue, with a thin 
coating of compact substance. The layer of compact bone which forms the 
articular surface, and to which the cartilage is attached, is called the articular 
lamella. It is of a white color, extremely dense, and varies in thickness. Its 
structure differs from ordinary bone tissue in this respect, that it contains no 
Haversian canals, and its lacunae are much larger than in ordinary bone and 
have no canaliculi The vessels of the cancellous tissue, as they approach the 
articular lamella, turn back in loops, and do not perforate it; this layer is conse- 
quently more dense and firmer than ordinary bone, and is evidently designed to 
form a firm and unyielding support for the articular cartilage. In the flat bones 
the articulations usually take place at the edges, and, in the short bones, at various 
parts of their surface. 

Cartilage. — There are three varieties of cartilage — ^1, hyaline; B, fibrocartilage; 
and C, yellow elastic cartilage; of these, but two, hyaline and fibrocartilage are 
utilized in the structure of a joint. 

In general, cartilage consists of a genetic investing membrane, the perichondrium, surrounding 
the cartilage substance proper. The latter consists of the cellular elements, or chondroblasts, 
and the intercellular substance, or matrix. 

The perichondrium is composed chiefly of white fibrous connecti^'e tissue ivith a few added 
yellow elastic fibres and cellular elements. The outer part contains few cells, and is called the 
fibrous layer. The inner part, or (jenetic Inijer, contains the bloodvessels, and is rich in flat- 
tened, elongated, or spindle-shaped cells, the chondroblasts. 

The chondroblasts vary in shape; those immediately beneath the perichondrium are flat 
and elongated, while those farther in become larger and o\'al in form. Each cell contains a 
prominent nucleus embedded in a clear protoplasm that may contain one or more vacuoles. 
Each cell is sharply outlined, and lies in a space called the lacuna, but two or more cells may be 
seen to occupy the same lacuna. The matrix immediately surrounding the lacuna is somewhat 
differentiated from the remaining matrix, and is called the capsule of the lacuna. 

(259) 



260 



THE ARTICULATIONS, OR JOINTS 



The matrix varies in the different varieties of cartilage. In hyaline cartilage it is bluish 
or ]5early in appearance, and under low magnification is apparently homogeneous; in the fibro- 
cartilage the matrix consists mainly of white fibrous tissue arranged in bundles of varying size 
with islands of hyaline matrix and cartilage cells at intervals; the matrix of elastic cartilage 
is mainly yellinv clastic lis.sue with islands of hyaline matrix and cartilage cells. 

A. Hyaline cartilage is surrounded by its perichondrium, internal to which is found the 
apparently homogeneous or slightly granular matrix. If the latter be examined by polarized 
light or be first treated with potassium hydrate, the fundamental fibrillse are discernible. The 
fibrils form a meshwork that contains the hyaline substance and cells. 

In joints the hyaline cartilage is found as a thin layer covering the articular surfaces of 
the bones concerned, and is here called articular cartilage. In this form the peripheral cells 
are parallel to the surface; deeper in toward the bone the cells become arranged in rows at 
right angles to the surface. The latter condition may account for the vertical splitting of articular 
cartilage that occurs in certain diseases. 

Hyaline cartilage is also found in the costal, tracheal, bronchial, and most of the larjmgeal 
cartilages. It tends to calcify and even ossify in old age, and upon boiling yields a substance 
called chondrin. 

The hyaline cartilage that covers the joint surfaces of the bones, by its elasticity enables it 
to break the force of any concussion, while its smoothness affords ease and freedom of move- 
ment. It varies in thickness according to the shape of the articular surface on which it lies; 
where this is convex the cartilage is thickest at the centre, where the greatest pressure is received; 
the reverse is the Case on the concave articular surfaces. 




: rr \'>-' __•==" 



g 






_.^ 



Fig. 213. — Sections of cartilage. A. Hyaline cartilage, a. Fibrous layer of perichondrium. 6. Genetic 
layer of perichondrium, c. Youngest chondroblasts. d. Older chondroblasts. e. Capsule, f. cells, g. Lacuna. 
B. Elastic cartilage. C. Wnite fibrocartilage. (Radasch.) 



5. Fibrocartilage is surrounded by a perichondrium; its matrix differs from that of the 
hyaline variety in consisting chiefly of white fibrous tissue arranged in bundles with little islands 
of hyaline substance and cells scattered here and there. It is found in the intra-articular car- 
tilages, deepening joint cavities, and in the intervertebral disks. It is arranged in three 
groups — (1) intra-articular, (2) connecting, and (.3) circumferential. 

1. The articular flbrocartilages, or articular disks (menisci artindares), are flattened, fibro- 
cartilaginous plates, of a round, oval, triangular, or sickle-like form, interposed between the 
articular cartilages of certain joints. They are free on both surfaces, thinner toward their 
centre than at their circumference, and held in position b}' the attachment of their margins 
and extremities to the surrounding ligaments. The synovial membrane of the joint is prolonged 
over them a short distance from their attached margins. They are found in the temporo- 
mandibular, sternoclavicular, acromioclavicular, wrist- and knee-joints. These cartilages are 



LIGAMENTS 261 

usually found in those joints which are most exposed to violent concussion and subject to fre- 
quent movements. Their use is to maintain the apposition of the ojjposed surfaces in their 
various motions; to increase the depth of the articular surfaces and give ease to the gliding 
movement; to moderate the effects of great pressure and deaden the intensity of the shocks to 
which the parts may be subjected. Iluraphry has pointed out that these intra-arlicular fil)ro- 
cartilages serve an important purpose in increasing the variety of movements in a joint. Thus, 
in the knee-joint there are two kinds of motion — viz., angular movement and rotation— although 
it is a hinge-joint, in which, as a rule, only one variety of motion is permitted; the former 
movement takes place between the condyles of the femur and the articular cartilages, the 
latter between the cartilages and the head of the tibia. So, also, in the temporomandibular 
joint, the upward and downward movement of opening and shutting the mouth takes place 
between the fibrocartilage and the mandible, the grinding movement between the glenoid cavity 
and the fibrocartilage, the latter moving with the mandible. 

Intra-articular cartilages may divide the joint into two distinct cavities, as in the temporo- 
mandibular articulation. The periphery of an articular cartilage is attached particularly to 
the capsule, and may also be attached to the nonarticular portion of the bone. The semilunar 
cartilages of the knee resemble tendon more than they do cartilage. The fibres are arranged 
in dense, more or less parallel bundles, separated by small, scattered hyaline cells, and the disks 
are attached to the bone by thin layers of hyaline cartilage. 

2. The connecting fibrocaitilages are interposed between the bony surfaces of those joints 
which admit of only slight moliility, as between the bodies of the vertebras and between the 
pubic bones. They form disks which adhere closely to both of the opposed surfaces, and are 
composed of concentric rings of fibrous tissue, with cartilaginous laminte interposed, the former 
tissue predominating toward the circumference, the latter toward the centre. 

3. The circumferential fibrocartilages consist of a rim of fibrocartilage, which surrounds the 
margin of sonu- ol' the ariicular caviiii-s, as the cotyloid cavity of the hip and the glenoid cavity 
of the shoulder; tliey serve (o deepen the articular surface, and to protect its edges. 

Elastic cartilage, although not utilized in joints, may be considered here. It is surrounded 
by a perichondrium, and its matrix differs from the preceding varieties in being composed 
chiefly of yellow elastic tissue. It is found in the pinna of the ear, Eustachian tube, epiglottis, 
and small cartilages of the larynx. It does not ossify or calcify. 

Cartilage, in the adult, is an avascular tissue, and although vessels at times are seen in the 
costal cartilages, they do not nourish it, as no branches are given off. Nerves are likewise 
absent. 

Ligaments consist of bands of various forms, serving to connect the articular 
extremities of bones, and are composed mainly of coarse bundles of very 
dense, white, fibrous tissue placed parallel with, or closely interlaced with, one 
another, and presenting a white, shining, silvery aspect. A ligament is pliant 
and flexible, so as to allow of the most perfect freedom of movement, but it is 
strong, tough, and inextensile, so as not readily to yield under the most severely 
applied force; it is consequently well adapted to serve as the connecting medium 
between the bones. Some ligaments consist entirely of yellow elastic tissue, as 
the ligamenta subflava, which connect together the adjacent arches of the verte- 
brae in man, and the ligamentum nuchae in the lower animals are composed of 
yellow elastic tissue. In these cases it will be observed that the elasticity of the 
ligament is intended to act as a substitute for muscular power. 

Synovial membrane is a thin, delicate, serous membrane, arranged in its 
simplest form like a short, wide tube, attached by its open ends to the margins 
of the articular cartilages and covering the inner surfaces of the various ligaments 
which connect the articulating surfaces, so that, along with cartilages, it completely 
encloses the joint-cavity. Its transudate is thick, viscid, and glairy, like the 
white of an egg, hence it is termed synovia. It is composed of a single layer of 
endothelial cells resting upon a thin layer of fibroelastic (subendothelial) tissue. 
The synovial membranes found in the body admit of subdivision into three kinds — 
articular, bursal, and vaginal. 

Articular synovial membrane is found in every freely movable joint. It lines the capsule 
of the joint and is reflected upon the nonarticular intracapsular portion of the bones which 
enter iiito the formation of the joint. In the fetus this membrane is said, by Toynbee, to 



262 



THE ARTICULATIONS, OR JOINTS 



be continued over the surface of the cartilages ; but in the adult it merely encroaches for a short 
distance upon the margins of the cartilages, to which it is firmly attached; it then invests the 
inner surface of the capsular or other ligaments enclosing the joint, and is reflected over the 
surface of any tendons passing through its cavity, as the tendons of the Popliteus in (he knee 
and the tendon of the Sleeps in the shoulder. In some of the joints the synovial membrane 
is thrown into folds, which pass across the cavity. They are called synovial ligaments, 
and are especially distinct in the knee. These folds, when large, frequently contain con- 
siderable quantities of fat, which acts as a cushion between the two articular surfaces and 
serves a valuable purpose in filling up gaps. In some joints there are flattened folds, sub- 
divided at their margins into fringe-like processes (sjoiovial villi), the vessels of which have 
a convoluted arrangement. These latter generally project from the synovial membrane near 
the margin of the cartilage and lie flat upon its surface. They consist of fibroelastic tissue 
covered with endothelium, and contain fat-cells in variable quantities, and, more rarely, isolated 
cartilage-cells. Under certain diseased conditions similar processes are found covering the 
entire surface of the synovial membrane, forming a mass of pedunculated fibrofatty growths 
which project into the joint. Similar structures are also found in some of the bursal and vaginal 
synovial membranes. 

The bursal synovial membranes are sacs interposed between surfaces w hich move upon each 
other, producing friction, as in the gliding of a tendon or of the integument o^er projecting bony 
surfaces. There are two groups of synovial bursse designated according to situation: (1) Sub- 
cutaneous synovial bursse {btirsae mucosae suhndaneae) (Fig. 214) are those situated between the 
integument and a prominent process of bone. Subcutaneous bursge are found between the 
integument and the front of the patella, over the olecranon, the malleoli, and other prominent 
parts. (2) Subtendinous synovial bursas (hursae mucosae subtendineae) (Fig. 214) are those situ- 
ated between tendons or muscles and the bony or cartilaginous surfaces over which the tendons 
or muscles glide. For example, a bursa is placed between the Glutei muscles and the surface 





Fig. 214. — Scheme of a serous bursa. (Poirier and Charpj-.) 



of the great trochanter. Subtendinous bursfe are found often about joints and not unusually com- 
municate directly with the cavity of the joint by means of an opening in the joint capsule, the 
synovial membrane of the joint being continuous with the synovial membrane of the bursa. 
For instance, the bursa between the tendon of the Psoas and Iliacus muscles and the capsular 
ligament of the hip communicates with the hip-joint; and the bursa between the under surface 
of the Subscapularis muscle and the neck of the scapula communicates with the shoulder-joint. 
Bursse consist of a thin wall of connective tissue, lined by endothelial cells, and contain a viscid 
fluid. 

The vaginal synovial membrane (Figs. 257 and 365), which is the synovial sheath or the 
thecal synovial bursa ( I'dt/tna mucosa tendinis), serves to facilitate the gliding of a tendon in the 
osseofibrous canal through \\hich it passes. The membrane is here arranged in the form of 
a sheath, one layer of which adheres to the w all of the canal, and the other is reflected upon the 
surface of the contained tendon, the space between the two surfaces of the membrane containing 
synovia. These sheaths are chiefly found surrounding the tendons of the Flexor and Extensor 
rnuscles of the fingers and toes as they pass through the osseofibrous canals in the hand or foot. 
A vaginal sheath covers the long head of the Biceps brachii muscle from its origin to the surgical 
neck of the humerus (Fig. 247). 

Subjacent to the synovial membrane of certain joints are found pads of adipose tissue, the 
synovial pads. These serve to fill up large spaces, and by adapting themselves to changes of 
position maintain the form of the joint during movement. 



SYNARTHROSIS 



2(53 



The articulations are divided into tliree classes — synarthrosis, or immovable; 
amphiarthrosis, or mixed; and diarthrosis, or movable joints. 

Synarthrosis (Immovable Articulation). — Synarthrosis includes all those artic- 
ulations in which tlie surfaces of the bones are in almost direct contact, being 
fastened together by an intervening mass of connective tissue, and in which there 



Sutural ligament 




Fig. 215, — Section across the sagittal suture. 



Cartilage 




Perichondrium 



-Section through the occipitosphenoid 
synchondrosis of an infant. 



is no joint cavity and no appreciable motion. Examples of synarthrosis are the 
joints between the bones of the cranium and of the face, excepting those of the 
mandible. The varieties of synarthrosis are four in number — sutura, schindylesis, 
gomphosis, and synchondrosis. 



Lifjament 
Intervertehral disk 
of fibrocartUage 




Articular cartilage -rT^?||%(Spo 

Fig. 217. — Diagrammatic section of a symphysis. 



The sutura is that form of articulation met with only in the skull, where the 
contiguous margins of flat bones are apparently but not really in immediate 
contact, a thin layer of fibrous tissue, sutural membrane, being interposed. This 
membrane is continuous externally with the pericranium and internally with the 




Articular cartilage 
Synovial membrane 
Capsular ligament 




Synovial membrane 

Articular cartilage 

Intra-articidar 
fibrocartUage 

Capsular ligament 



Fig. 219. — Diagrammatic section of a diarthrodial 
joint, with an intra-articular fibrocartilage. 



dura. In some of the sutures the sutural membrane gradually disappears as 
age advances and the two bones form an osseous fusion. Where the articulating 
surfaces are connected by a series of processes and indentations interlocked. 



264 THE ARTICULATIONS, OB JOINTS 

it is termed a true suture, or sutura vera, of which there are three varieties — sutura 
dentata, serrata, and limbosa. The sutura dentata is so called from the tooth-liive 
form of the projecting articular processes, as in the suture between the parietal 
bones. In the sutura serrata the edges of the two bones forming the articulation 
are serrated like the teeth of a fine saw, as between the two portions of the frontal 
bone. In the sutura limbosa besides the dentated processes, there is a certain 
degree of bevelling of the articular surfaces, so that the bones overlap each other, 
as in the suture between the parietal and frontal bones. When the articulation 
is formed by roughened surfaces placed in apposition with one another, it is 
termed the false suture, of which there are two kinds — the sutura squamosa, formed 
by the overlapping of two contiguous bones by broad bevelled margins, as in the 
squamoparietal (squamous) suture; and the sutura harmonia, where there is simple 
apposition of two contiguous, rough, bony surfaces, as in the articulation between 
the two maxilla; or of the horizontal plates of the palate bones. 

Schindylesis is that form of articulation in which a thin plate of bone is 
received into a cleft or fissure formed by the separation of two laminse in another 
bone, as in the articulation of the rostrum of the sphenoid and perpendicular 
plate of the ethmoid mth the vomer, or in the reception of the latter in the 
median fissure between the maxillse and palate bones. i 

A gomphosis is an articulation formed by the insertion of a conical process 
into a socket, as a nail is driven into a board; this is not illustrated by any articu- 
lation between bones, properly so called, but is seen in the articulation of the teeth 
with the alveoli of the maxillae and mandible. 

A synchondrosis is a joint in which the connecting medium is hyaline cartilage. 
This is a temporary form of joint, because the hyaline cartilage becomes con- 
verted into bone before adult life. Such joints are found between the epiphyses 
and shafts of long bones, between the occipital and the sphenoid at, and for some 
years after birth. 

Amphiarthrosis (Mixed Articulation). — In this form of articulation the con- 
tiguous osseous surfaces are either connected by broad flattened disks of fibro- 
cartilage which adhere to the end of each bone, as in the articulation between the 
bodies of the vertebrae, or else the articular surfaces are co^'ered with fibro- 
cartilage, partially lined by synovial membrane, and connected by external liga- 
ments, as in the pubic symphysis, both of these joints being capable of limited 
motion. 

The articulation between the bodies of the vertebrae resemble the synarthrodia! 
joints in the continuity of their surfaces and the absence of a synovial sac; the 
symphysis pubis resembles the diarthrodial articulation. 

Diarthrosis (Movable Articulation). — This form of articulation includes the 
greater number of the joints in the body, mobility being their distinguishing 
character. They are formed by the approximation of two contiguous bony 
surfaces covered with cartilage, connected by ligaments and lined with synovial 
membrane. The varieties of joints in this class have been determined by the 
kind of motion permitted in each. There are two varieties in which the move- 
ment is uniaxial; that is to say, all movements take place around one axis. In 
one form, the ginglymus, or hinge-joint, this axis is, practically speaking, trans- 
verse; in the other, the trochoid, or pivot-joint, it is longitudinal. There are two 
varieties where the movement is biaxial or around two horizontal axes at right 
angles to each other or at any intervening axis between the two. These are the 
condyloid joint and the saddle-joint. There is one form of joint where the move- 
ment is polyaxial, the enarthrosis, or ball-and-socket joint. And finally there are 
the arthrodia, or gliding joints. In a diarthrosis there is always a joint cavity 
lined with synovial membrane — the articular surfaces of the bones are covered 
with hyaline cartilage, and the bones are held in contact by ligaments. 



S VNA B TIIR OSIS 265 

The ginglymus, or hinge-joint, is that form of joint in which the articular surfaces 
are moulded to eacii other in such a manner as to permit motion only in one plane, 
forward and backward; the extent of motion at the same time being coi^siderahle. 
The direction which the distal bone takes in this motion is never in the same 
plane as that of the axis of the proximal bone, and there is always a certain amount 
of alteration from the straight line during flexion. The articular surfaces are 
connected together by strong lateral ligaments, which form their chief bond of 
union. The most perfect forms of ginglymus are the interphalangeal joints. 

A trochoid, or pivot-joint or rotary joint, is one in which the movement is 
limited to rotation; the joint is formed by a pivot-like process turning within 
a ring, or the ring on the pivot, the ring being formed partly of bone, partly of 
ligament. In the superior radioulnar articulation the ring is formed partly by 
the lesser sigmoid cavity of the ulna and in the rest of its extent by the orbicular 
ligament; here the head of the radius rotates within the ring. In the articulation 
of the odontoid process of the axis with the atlas the ring is formed in front by 
the anterior arch of the atlas; behind, by the transverse ligament; here the ring 
rotates around the odontoid process. 

Condyloid or biaxial articulation is that form of joint in which an ovoid artic- 
ular head, or condyle, is received into an elliptical cavity in such a manner as 
to permit of flexion and extension, adduction and abduction and circumduction, 
but no axial rotation. The articular surfaces are connected together by anterior, 
posterior, and lateral ligaments. An example of this form of joint is found in 
the wrist. 

Articulation by reciprocal reception, or saddle-joint, is that variety in which the 
articular surfaces are concavo-convex; that is to say, they are inversely convex 
in one direction and concave in the other. The movements are the same as in 
the preceding form; that is to say, there is flexion, extension, adduction, abduction, 
and circumduction, but no axial rotation. The articular surfaces are connected 
by a capsular ligament. The best example of this form of joint is the carpo- 
metacarpal joint of the thumb. 

An enarthrosis, or ball-and-socket joint, is that form of joint in which the distal 
bone is capable of motion around an indefinite number of axes which have one 
common centre. It is formed by the reception of a globular head into a deep 
cup-like cavity, the parts being kept in apposition by a capsular ligament strength- 
ened by accessory ligamentous bands. Examples of this form of articulation are 
found in the hip- and shoulder-joints. 

Arthrodia. — Arthrodia is that form of joint which admits of a gliding move- 
ment; it is formed by the approximation of plane surfaces or of one slightly con- 
cave to one slightly convex, the amount of motion between them being limited 
by the ligaments, or osseous processes, surrounding the articulation; as in the 
articular processes of the vertebrte, the carpal joints, except that of the os magnum 
with the scaphoid and semilunar bones. 

Below, in tabular form, are the names, distinctive characters, and examples 
of the different kinds of articulations: 



266 



IHE ARTICULATIONS, OR JOINTS 



Synarthrosis, or Im- 
movable Joint. Sur- 
faces separated by 
fibrous membrane or 
by a line of cartilage, 
without any interven- 
ing synovial cavity, 
and immovably con- 
nected 'with each 
other. 

As in joints of cran- 
ium and face (except 
mandible). 



Amphiarthrosis, 
Mixed Articulation. 



Suiura. Articu- 
lation by processes 
and indentations '' 
interlocked. 



Diarthrosis, 
^Movable Joint. 



f Dentaia, having tooth- 
I like processes. 
I As in interparietal suture. 
Serrata, having serrated 
Sutura vera (true) I ^'^S^^ ^'^^ ^^ ^eeth of a 
articulate bv indent- -1 ^^^'' ... 
ed borders. " "^ mtertrontal suture. 

Limbosa, having bevelled 
margins and dentated pro- 
cesses. 

As in frontoparietal su- 
l ture. 

I Squamosa, formed by 
thin bevelled margins, over- 
lapping each other. 
Sutura notha ^J"^^ ''^ squamoparietal 

(false), articulate hy { tt ' ■ „ , , 

UP ■' ' Harmonia, formed bv 

rough surfaces. ^, .,.' „ . •■ 

" the apposition of contigu- 

ous rough surfaces. 

As in intermaxillary su- 
[ ture. 

Schindylesis. — Articulation formed by the reception of a thin plate 
of one bone into a fissure of another. 

As in articulation of rostrum of sphenoid with vomer. 

Gomphosis. — Articulation formed by the insertion of a conical process 
into a socket — the teeth. 

Synchondrosis — (1) Surfaces connected by fibrocartilage and not 
separated by synovial membrane. Has limited motion. As in joints 
between bodies of vertebrse. 

(2) Surfaces covered by fibrocartilage, lined by partial synovial 
membrane. As in pubic symphysis. 

Ginglymus. — Hinge-joint; motion limited to two directions, for- 
ward and backward. Articular surfaces fitted together so as to 
permit of movement in one plane. As in the interphalangeal 
joints. 

Trochoid, or Pivoi-joint. — Articulation by a pivot process turning 
within a ring or ring around a pivot. As in superior radioulnar articu- 
lation and atlanto-axial joint. 

Condyloid. — Ovoid head received into elliptical cavity. Movements 
in every direction except axial rotation. As the wrist-joint. 

Reciprocal Reception (saddle-joint). — Articular surfaces inversely con- 
vex in one direction and concave in the other. Movement in e\"ery 
direction except axial rotation. As in the carpometacarpal joint of the 
thumb. 

Enart.hrosis. — Ball-and-socket joint ; capable of motion in all directions. 
Articulations by a globular head received into a cup-like cavity. As in 
hip- and shoulder-joints. 

Arthrodia. — Gliding joint; articulations by plane surfaces, which 
glide upon each other. As in carpal and tarsal articulations. 



The Einds of Movement Admitted in Joints. 



The movements admissible in the joints may be divided into four kinds — ghding, 
angular movement, circumduction, and rotation. These movements are often, 
however, more or less combined in the various joints, so as to produce an infinite 
variety, and it is .seldom that we find only one kind of motion in any particular 
joint. 

Gliding movement is the most simple kind of motion that can take place in a 
joint, one surface gliding or moving over another without any angular or rotatory 
movement. It is common to all movable joints, but in some, as in the articu- 
lations of the carpus and tarsus, it is the only motion permitted. This movement 
is not confined to plane surfaces, but may exist between any two contiguous 



TliU KINDS OF MO VE3IENT ADMITTED IN JOINTS 2G7 

surfaces, of whatever form, limited by the ligaments which enclose the articu- 
lation. Gliding over a wide range, as is seen in the sliding of the patella over 
the condyles of the femur, is called coaptation. 

Angular movement occurs only between the long bones, and by it the angle 
between the two bones is increased or diminished. It may take place in four 
directions — forward and backward, constituting flexion or bending and extension 
or straightening, or inward toward and outward from the medial line of the body, 
constituting adduction and abduction. Al)duction of a limb is movement away 
from the medial line of the body. Adduction of a limb is movement toward the 
medial line of the body. In the fingers and toes the significance of the terms are 
different; abduction means movement of the fingers away from the middle finger 
or of the toe away from the second toe; adduction means movement of fingers 
toward the middle finger or of the toes toward the second toe. The strictly gingly- 
moid or hinge-joints admit of flexion and extension only. Abduction and adduc- 
tion, combined with flexion and extension, are met with in the more movable 
joints; as in the hip-, shoulder-, and metacarpal-joint of the thumb, and partially 
in the wrist. When two anterior surfaces are brought nearer together, as by 
bending the elbow or wrist, we speak of the movement as anterior or ventral 
flexion. Ventral flexion of the wrist is also called volar or palmar flexion. If 
two posterior surfaces are brought nearer together, as by bending the knee or 
extending the wrist, we speak of the movement as posterior or dorsal flexion. 

At the wrist-joint the bending of the ulnar margin of the hand toward the 
ulnar side of the forearm is ulnar flexion; the bending of the radial margin of 
the hand toward the radial side of the forearm is radial flexion. 

Circumduction is that limited degree of motion which takes place between the 
head of the bone and its articular cavity, while the extremity and sides of the limb 
are made to circumscribe a conical space, the base of which corresponds with the 
inferior extremity of the limb, the apex with the articular cavity; this kind of 
motion is best seen in the shoulder- and hip-joints. 

Rotation is the movement of a bone upon an axis, which is the axis of the pivot 
on which the bone turns, as in the articulation between the atlas and axis, when 
the odontoid process serves as a pivot around which the atlas turns; or else is the 
axis of a pivot-like process which turns within a ring, as in the rotation of the 
radius upon the humerus. 

Ligamentous Action of Muscles. — The movements of the different joints of a limb are com- 
bined by means of the long muscles which pass over more than one joint, and which, when 
relaxed and stretched to their greatest extent, act as elastic ligaments in restraining certain 
movements of one joint, except when combined with corresponding movements of the other, these 
latter movements being usually in the opposite direction. Thus, the shortness of the Hamstring 
muscles prevents complete flexion of the hip, unless the knee-joint is also flexed, so as to bring 
their attachments nearer together. The uses of this arrangement are threefold : (1 ) It coordinates 
the kinds of movement which are the most habitual and necessary, and enables them to be per- 
formed with the least expenditure of power. "Thus, in the usual gesture of the arms, whether 
in grasping or rejecting, the shoulder and the elbow are fiexed simultaneously, and simultaneously 
extended," in consequence of the passage of the Biceps and Triceps brachii over both joints. 
(2) It enables the short muscles which pass over only one joint to act upon more than one. "Thus, 
if the Rectus femoris remain tonically of such length that, when stretched over the extended hip, 
it compels extension of the knee, theia the Gluteus maximus becomes not only an extensor of the 
hip, but an extensor of the knee as well." (3) It provides the joints with ligaments which, while, 
they are of very great power in resisting movements to an extent incompatible with the mechan- 
ism of the joint, at the same time spontaneously yield when necessary. "Taxed beyond its 
strength, a ligament will be ruptured, whereas a contracted muscle. is easily relaxed; also, if 
neighboring joints be united by ligaments, the amount of flexion or extension of each must remain 
in constant proportion to that of the other; while, if the union be by muscles.the seijaration of 
the points of attachment of those muscles may vary considerably in different varieties of move- 
ment, the muscles adapting themselves tonically to the length required."' Dr. W. W. Keen 
points out how important it is " that the stu-geon should remember this ligamentous action of 

' Dr. Cleland, in Journal of Anatomy and Physiology, 1S66, No. 1, p. 85. 



268 THE ARTICULATIONS, OR JOINTS 

muscles in making passive motion — for instance, at tlie wrist after Colles' fracture. If the 
fingers be extended, tlie wrist can be fiexed to a right angle. If, however, thev be first flexed, 
as in 'making a fist.' flexion at the wrist is stricti}' limited to from 40 to 50 degrees in difTerent per- 
sons, and is very painful beyond that point. Hence, passive motion here should be made with 
the fingers extended. In the leg, when flexing the hip, the knee should be flexed." Dr. Keen 
further points out that "a beautiful illustration of this is seen in the perching of birds, whose 
toes are forced to clasp the perch by just such a passive ligamentous action so soon as they 
stoop. Hence, they can go to sleep and not fall off the perch." 

The articulations may be arranged into those of the trunk, those of the upper 
extremity, and those of the lower extremity. 



ARTICULATIONS OF THE TRUNK. 

These may be divided into the following groups, viz. : 



I. Of the Vertebral Column. 
II. Of the Atlas with the Axis. 

III. Of the Atlas with the Occipital 

Bone. 

IV. Of the Axis with tiae Occipital Bone. 
V. Of the Mandible. 

VI. Of the Ribs with the Vertebrae. 



VII. Of the Cartilages of the Ribs with 
the Sternum and with Each 
Other. 
VIII. Of the Sternum. 
IX. Of the Vertebral Column with the 

Pelvis. 
X. Of the Pelvis. 



I. Articulations of the Vertebral Column. 

The different segments o*^ the vertebral column are connected by spinal ligaments 
iQigamenta coluninae vertehralis), which may be divided into five sets: (1) Those 
connecting the bodies of the vertebrse. (2) Those connecting the laminae. (3) 
Those connecting the articular processes. (4) Those connecting the spinous processes. 
(5) Those of the transverse processes (the last four kinds being known as interneural) . 

The articulations of the bodies of the vertebrfe with each other form a series 
of amphiarthrodial joints; those between the articular processes form a series of 
arthrodial joints. 



1. Ligaments of the Vertebral Bodies or Centra (Intercentral 

Ligaments). 

Anterior Common Ligament. 
Posterior Common Ligament. 
Intervertebral Substance. 

The anterior common ligament {Ugamentum longitidinale anterms) (Figs. 
222, 225, and 228) is a broad and strong band of longitudinal fibres which extends 
along the anterior (ventral) surface of the bodies of the vertebrfe from the axis 
to the sacrum. It is broader below than above, thicker in the thoracic than in 
the cervical or lumbar regions, and somewhat thicker opposite the front of the 
body of each vertebra than opposite the intervertebral substance. It is attached, 
above, to the body of the axis by a pointed process, where it is continuous with the 
.anterior atlanto-axial ligament, is connected with the tendon of insertion of the 
Longus colli muscle, and extends down as far as the upper bone of the sacrum. 
It consists of dense longitudinal fibres, which are intimately adherent to the 
^intervertebral substance and the prominent margins of the vertebrfe, but less 



ARTICULATIONS OF THE VERTEBRAL COLUMN 



269 



closely to the middle of the bodies. In the latter situation the fibres are exceed- 
ingly thick, and serve to fill up (he concavities on their front surface and to make 
the anterior surface of the vertebral column more even. This ligament is com- 
posed of several layers of fibres, which vary in length, but are closely interlaced 
with each other. The most superficial or longest fibres extend between four or 
five vertebrse. A second subjacent set extends between two or three vertebrte, 
while a third set, the shortest and deepest, extends from one vertebra to the next. 
At the side of the bodies the ligament consists of a few short fibres, which pass 
from one vertebra to the next, separated from the median portion by large oval 
apertures for the passage of vessels. 

The posterior common ligament {ligamentum lomjitudinale posferius) (Figs. 
227 and 228) is situated within the vertebral canal, and extends along the posterior 
(dorsal) surface of the liodies of the vertebrae from the body of the axis above, where 




nterverte- 
jral fibro- 
:artilage 




LIGAMENT 

-Vertebral bodies with ligaments 
behind. (Spalteholz.) 



ith the adjacent. 
(Spalteholz.) 



it is continuous with the posterior occipito- 
axial ligament, to the sacrum below. It is 
broader above than below, and thicker in 
the thoracic than in the cervical or lumbar 
regions. In the situation of the interver- 
tebral substance and contiguous margins 
of the vertebrfe, where the ligament is more intimately adherent, it is broad, and 
presents a series of dentations with intervening concave margins; but it is narrow 
and thick over the centre of the bodies, from which it is separated by the vente 
basis vertebrte. This ligament is composed of smooth, shining, longitudinal 
fibres, denser and more compact than those of the anterior ligament, and formed 
of a superficial layer occupying the interval between three or four vertebrre, and 
of a deeper layer which extends between one vertebra and the next adjacent 
to it. It is separated from the dura of the spinal cord by loose connective tissue. 
The Intervertebral Fibrocartilages {fibrocartilagines inienertebralcs) (Figs. 
221 and 222). — Each fibrocartilaginous disk is of lenticular form and of composite 
structure. The disks are interposed between the adjacent surfaces of the bodies 
of the vertebrse from the axis to the sacrum, and form the chief bonds of connec- 
tion between those bones. In young children intervertebral substance exists 
in the coccyx. These disks vary in shape, size, and thickness in dift'erent parts 
of the vertebral column. In shape they accurately correspond with the surfaces 
of the bodies between which they are placed, being oval in the cervical and lumbar 
regions, and circular in the thoracic. Their size is greatest in the lumbar region. 



270 THE ABTJCULATIONS, OB JOINTS 

In thickness they vary not only in the different regions of the vertebral column, 
but in different parts of the same disk; thus, they are thicker in front than behind 
in the cervical and lumbar regions, while they are uniformly thick in the thoracic 
reo-ion. The intervertebral disks form about one-fourth of the vertebral column, 
exclusive of the first two vertebrae; they are not equally distributed, however, 
between the various bones; the thoracic portion of the vertebral column having, 
in proportion to its length, a much smaller quantity than in the cervical and lumbar 




right half of sectic 



regions, which necessarily gives to the latter parts greater pliancy and freedom 
of movement. The intervertebral disks are adherent, by their surfaces, to a 
thin layer of hyaline cartilage which covers the upper and under surfaces of the 
bodies of the vertebrse, and in which, in early life, the epiphyseal plates develop, 
and by their circumference are closely connected in froat to the anterior, and 
behind to the posterior common ligament; while in the thoracic region they 
are connected laterally, by means of the interarticular ligament, to the heads of 
those ribs which articulate with two vertebrae; they, consequently, form part of 
the articular cavities in which the heads of these bones are received. 

Structure of the Intervertebral Substance. — The outer portion of the intervertebral sub- 
stance is composed of many layers of fibrous connective tissue. This enveloping; portion is called 
the annulus fibrosus. The central portion of the disk is composed of soft, pulpy, highly elastic 
fibrocartilage, containing some bands of connective tissue. It is called the nucleus pulposus, is of 
a yellowish color, and rises up considerably above the surrounding level when the ilisk is divided 
horizontally. This pulpy substance, which is especially well developed in the lumliar region, 
is the remains of the notochord, and, according to Luschka, contains a small synovial cavity in its 
centre. The outer layers of the disk are arranged concentrically one within the other, the outer- 
most consisting of ordinary fibrous tissue, but the others and more numerous consisting of white 
fibrocartilage. These plates are not quite vertical in their direction, those near the circumference 
being curved outward and closely approximated; while those nearest the centre curve in the 
opposite direction, and are somewhat more widely separated. The fibres of which each plate is 
composed are directed, for the most part, obliquely from above downward, the fibres of adjacent 
plates passing in opposite directions and varying in every layer; so that the fibres of one layer 
are directed across those of another, like the limbs of the let'tei; X. This laminar arrangement 
belongs to about the outer half of each disk. The pulpy substance presents no concentric arrange- 
ment, and consists of a fine fibrous matrix, containing angular cells, united to form a reticular 



ARTICULATIONS OF THE VERTFAiBAL COLUMN 



271 



structure. J. Bland Sutton' calls attention to the fact that in the human fetus a transverse 
ligamentous band crosses the dorsal aspect of the intervertebral disk and is continuous with the 
interosseous ligaments of the heads of the riljs; and also that a fetal ligamentous band exists in 
the ventral surface of the intervertelwal disiv which, after development, becomes the middle 
fasciculus of the stellate ligament. These liands are named by Sutton the posterior conjugal 
ligaments and the anterior conjugal ligaments. 

Intemeural articulations inciiule tiie ligaments of the laminse; articular pro- 
cesses, spinous processes, and transverse processes. 



2. Ligaments Connecting the Lamin.e. 



Ligamenta Subflava. 

•The ligamenta subflava {Ibjamenta intercmralia) (Figs. 222 and 223) are inter- 
posed between the lamina? of the vertebrse, from the axis to tlie sacrum. They 
are most distinct wlien seen from tlie interior of tlie vertebral canal; when viewed 
from the outer surface they ap- 
pear sliort, being overlapped by 
the laminae. Each ligamentum 
subfiavum consists of two lateral 
portions, which commence on 
each side at the root of either 
articular process, and pass back- 
ward to the point where the 
laminfe converge to form the 
spinous process, where their mar- 
gins are in contact and to a 
certain extent united; slight in- 
tervals being left for the passage 
of small vessels. These ligaments 
consist of yellow elastic tissue, 
the fibres of which, almost per- 
pe:idicular in direction, are at- 
tached to the anterior surface of 
the laminse above, some distance 
from its inferior margin, and to 
the posterior surface, as well as 
to the margin of the lamina 
below. In the cervical region 
they are thin in texture, but very 
broad and long; they become 
thicker in the thoracic region, 
and in the lumbar acquire very 
considerable thickness. Their 
highly elastic property serves to 
preserve the upright posture and to assist in resuming it after the spine has been 
flexed. These ligaments do not exist between the occiput and atlas or between 
the atlas and axis. 




3. Ligaments Connecting the Articular Processes. 
Capsular Ligaments. 

The capsular ligaments {ca-psidae articiikires) (Fig. 225) are thin and loose 
ligamentous sacs, attached to the contiguous margins of the articulating processes 

• Ligaments: Their Nature and Morphology, 1887. 



272 



THE ARTICULATIONS, OR JOINTS 



of each vertebra through the greater part of their circumference, and completed 
internally by the ligamenta subflava. They are longer and looser in the cervical 
than in the thoracic or lumbar regions. The capsular ligaments are lined on 
their inner surface with synovial membrane. 

4. Ligaments Connecting the Spinous Processes. 

Supraspinous Ligament. 
Ligamentum Nuchae. 
Interspinous Ligaments. 

The supraspinous ligament (ligamentum sicprasfinale (Fig. 222) is a strong 
fibrous cord, which connects the apices of the spinous processes from the seventh 
cervical to the spinous processes of the sacrum. It is thicker and broader in 
the lumbar than in the thoracic region, and intimately blended, in both situa- 
tions, with the neighboring aponeurosis. The most superficial fibres of this 
ligament connect three or four vertebrae; those deeper-seated pass between two 
or three vertebrae; while the deepest connect the contiguous extremities of neigh- 
boring vertebrae. It is continued upward to the external occipital protuberance 
as the ligamentum nuchae. 

The ligamentum nuchae is a fibrous membrane which, in the neck, represents 
the supraspinous ligaments of the lower vertebrte. It extends from the external 
occipital protuberance and crest to the spinous process of the seventh cervical 
vertebra. From its anterior border a fibrous lamina is given off, which is attached 
to the posterior tubercle of the atlas, and to the spinous processes of all the cervical 
vertebrae, so as to form a septum between the muscles on either side of the neck. 
In man it is merely a rudiment of an important elastic band which, in some of 
the lower animals, serves to sustain the weight of the head. 

The interspinous ligaments {ligamenta interspinalia) (Fig. 222), thin and 
membranous, are interposed between the spinous processes. Each ligament 
extends from the root to the summit of each spinous process and connects their 
adjacent margins. They meet the ligamenta subflava in front and the supraspin- 
ous ligament behind. They are narrow and elongated in the thoracic region; 
broader, Cjuadrilateral in form, and thicker in the lumbar region; and only slightly 
developed in the neck. 

5. Ligaments Connecting the Transverse Processes. 

Intertransverse Ligaments. 

The intertransverse ligaments {ligamenta intertransversaria) (Fig. 235) consist 
of bundles of fibres interposed between the transverse processes. In the cervical 
region they consist of a few irregular, scattered fibres; in the thoracic, they are 
rounded cords intimately connected with the deep muscles of the back; in the 
lumbar region they are thin and membranous. 

Movements of the Vertebral Column. — The movements permitted in the vertebra 
column are flexion, exteiision, lateral movement, circumduction, and rotation. 

In flexion (forward flexion), or movement of the vertebral column forward, the anterior 
common ligament is rela.\ed, and the intervertebral substances are compressed in front, while 
the posterior common ligament, the ligamenta subflava, and the inter- and supraspinous liga- 
ments are stretched, as well as the posterior fibres of the intervertebral disks. The interspaces 
between the laminte are widened, and the inferior articular processes of the vertebrse above 
glide upward upon the articular processes of the vertebrae below. Flexion is the most extensive 
of all the movements of the vertebral column. 

In extension (backward flexion), or movement of the vertebral column backward, an exacdy 
opposite disposition of the parts take place. This movement is not extensive, being limited 
by the anterior common ligament and by the approximation of the spinous processes. 



ARTICULATION OF THE ATLAS WITH THE AXIS 



273 



Flexion and extension are greatest in the lower part of the lumbar region between the third 
and fourth and fourth and fifth lumbar vertebroe; above the third they are much diminished, 
and reach their minimum in the middle and upper part of the back. They increase again in the 
neck, the capability of motion backward from the upright position being in this region greater 
than that of the motion forward, whereas in the lumbar region the reverse is the case. 

In lateral flexion, the sides of the interveitebral disks are compressed, the extent of motion 
being liiiiiicd by the resistance offered by the surrounding ligaments and by the approximation 
of the traiisxcrse i)rocesses. This movement may take place in any part of the vertebral column, 
but has the greatest range in the neck and loins. 

Circumduction is limited, and is produced merely by a succession of the preceding movements. 

Rotation is produced by the twisting of the intervertebral substances; this, although only 
slight between any two vertebrre, produces a considerable extent of movement when it takes 
place in the whole length of the vertebral column, the front of the upper part of the column 
being turned to one or the other side. This movement takes place only to a slight extent in the 
neck, but is more .pronounced in the upper part of the thoracic region, and is altogether absent in 
the lumbar region. It is thus seen that the cervical region enjoys the greatest extent of each 
variety of movement, flexion and extension, especially, being very extensive. In the thoracic 
region the three movements of flexion, extension, and circumduction are permitted only to a 
slight extent, while rotation is very extensive in the upper part and ceases below. In the lumbar 
region there is extensive flexion, extension, and lateral movement, but no rotation. 

The movements permitted are mainly due to the shape and position of the articulating pro- 
cesses. In the loins the inferior articulating processes are turned outward and are embraced by 
the superior; this renders rotation in tliis region of the vertebral column impossible, while there is 
nothing to prevent a sliding upward and downward of the surfaces on each other, so as to allow 
of flexion and extension. In the thoracic region, on the other hand, the articulating processes, by 
their direction and mutual adaptation, especially at the upper part of the series, permit of rotation, 
but prevent extension and flexion, while in the cervical region the greater obliquity and lateral 
slant of the articular processes allow not only flexion and extension, but also rotation. 

The principal muscles which produce flexion are the Sternomastoid, Rectus capitis anticus 
major, and Longus colli ; the Scaleni ; the abdominal muscles and the Psoas magnus. Extension 
is produced by the fourth layer of the muscles of the back, assisted in the neck by the Splenius, 
Semispinales dorsi et colli, and the Multifidus spinae. Lateral motion is produced by the fourth 
layer of the muscles of the back, by the Splenius and the Scaleni, the Quadratus lumborum 
and Psoas magnus, the muscles of one side only acting; and rotation by the action of the fol- 
lowing muscles of one side only — viz., the Sternomastoid, the Rectus capitis anticus major, the 
Scaleni, the Multifidus spinae, the Complexus, and the abdominal muscles. 

II. Articulation of the Atlas with the Axis (Articulatio Atlantoepistrophica). 

The articulation of the atlas with the axis is of a complicated nature, compris- 
ing no fewer than four distinct joints. There is a pivot articulation between the 
odontoid process of the axis and the ring formed between the anterior arch of 




Fig. 224. — Articulation between odontoid process and atlaa. 



the atlas and the transverse ligament (Fig. 224). Here there are two joints — one 
in front between the posterior surface of the anterior arch of the atlas and the front 

18 



274 



THE ARTICULATIONS, OR JOINTS 



of the odontoid process (atlanto-odontoid joint); the other between the anterior 
surface of the transverse ligament and the back of the process (syndosmo-odon- 
toid joint). Between the articular processes of the two bones there is a double 
arthroidal or gliding joint. The ligaments which connect these bones are the 



Anterior Atlanto-axial. 
Posterior Atlanto-axial. 



Transverse. 
Two Capsular. 



The anterior atlanto-axial ligament (Figs. 225 and 228) is a strong, membranous 
layer, attached, above, to the lower border of the anterior arch of the atlas; below, 
to the base of the odontoid process and to the front of the body of the axis. It is ■ 
strengthened in the middle line by a rounded cord, which is attached, above, 
to the tubercle on the anterior arch of the atlas, and heloiv to the body of the axis, 
being a continuation upward of the anterior common ligament of the vertebral 
column. The ligament is in relation, in front, with the Recti antici majores. 

The posterior atlanto-axial ligament (Figs. 225 and 228) is a broad and thin 
membranous layer, attached, above, to the lower border of the posterior arch 
of the atlas; below, to the upper edge of the laminte of the axis. This ligament 
supplies the place of the ligamenta subflava, and is in relation, behind, with the 
Inferior oblique muscles. 

The transverse ligament of the atlas' (ligamentum transversum atlantis) (Figs. 
227 and 228) is a thick, strong band, which arches across the ring of the atlas, 
and serves to retain the odontoid process in firm connection with its anterior 



«L LIGAMENT f "^'^ rtl'Sj 



ANTERIOR CONDYLAR 



Fig. 225. — Occipital bone 




TRANSVERSE 

CESS OF 
ATLAS 



JOIN- 


r BETWEEI 


lODY Of 


■VERT 


"EBR 


AND 


INTEI 


=tVER 


TEBHAL F 


IBRO 




CARTI 


LAGI 



TRANSVERSE PROCESS 
THrRD CERVICAL 
HTEBRA 



ical vertebra with ligaments, from in front. (Spalteholz.) 



arch. This ligament is flattened from before backward, broader and thicker in 

st,',rw''^n,?r»!S^^t°''tr^t"f •*" describe the transverse ligament with those of the atlas and axis; but the 
?h^ ,forteb.,1 n^t^^"'''''' *''*, 'I '5 ™''"^ ^ •i°''"°" °f 'he mechanism by which the movements of the head on 
«?;l'/^LTlire\trw;?nt£i1^tt^e°r*b^ "^<^ ^"^^ '^^ ^^^ --^^^ ^'^^^^ '<> "-^ ^'^^^^ 



ARTICULATION OF THE ATLAS WITH THE OCCIPITAL BONE 275 

the middle than at either extremity, and firmly attached on each side to a small 
tubercle on the inner surface of the lateral mass of the atlas. As it crosses the 
odontoid process, a small fasciculus is derived from its upper, and another from 
its lower border; the former passing upward, to be inserted into the anterior sur- 
face of the foramen magnum of the occipital bone; the latter, downward, to be 
attached to the posterior surface of the body of the axis; hence, the whole ligament 
has received the name of cruciform ligament {Ugamentum cnwiahim atlantis). 
A synovial surface is interposed between the odontoid process and the trans- 
verse ligament, and one is placed between the anterior surface of the odontoid 
process and the anterior arch of the atlas. The transverse ligament divides the 
vertebral foramen of the atlas into two unequal compartments; of these, the pos- 
terior and larger serves for the transmission of the cord and its membranes and 
the spinal accessory nerves; the anterior and smaller contains the odontoid pro- 
cess. Since the space between the anterior arch of the atlas and the transverse 
ligament is smaller at the lower part than the upper (because the transverse 
lio-ament embraces tightly the narrow neck of the odontoid process), this process 
is retained in firm connection with the adas after all the other ligaments have been 
divided. 

The capsular ligaments (capsulae articulares) (Figs. 226 and 227) are two thin 
and loose capsules, connecting the lateral masses of the adas with the superior 
articular surfaces of the axis, the fibres being strengthened at the posterior and 
inner part of each articulation by an accessory ligament, which is attached below 
to the body of the axis near the base of the odontoid process. 

Synovial Membranes (Fig. 224). — There are four sjoiovial membranes in this articulation — 
one linhig; the inner surface of each of the capsular Hgaments; one between the anterior surface 
of the odontoid process and- the anterior arch of the atlas; and one between the posterior surface 
of the odontoid process and the transverse ligament. The latter often communicates with 
those between the condyles of the occipital bone and the articular surfaces of the atlas. 

Movements. — This joint allows the rotation of the atlas (and, with it, of the cranium) upon 
the axis, the extent of rotation being limited by the odontoid ligaments. 

The principal muscles by which this action is produced are the Sternomastoid and Com- 
plexus of one side, acting with the Rectus capitis anticus major, Splenius, Trachelomastoid, 
Rectus capitis posticus major, and Inferior oblique of the other side. 



ARTICULATIONS OF THE VERTEBRAL COLUMN WITH THE CRANIUM. 

The ligaments connecting the vertebral column with the cranium may be divided 
into two sets — those connecting the occipital bone with the atlas, and those con- 
necting the occipital bone with the axis. 

III. Articulation of the Atlas with the Occipital Bone (Articulatio 
Atlanto-occipitalis) . 

This articulation is a double condyloid joint. Its ligaments are the 

Anterior Occipito-atlantal. Posterior Occipito-atlantal. 

Two Capsular. 

The anterior occipito-atlantal ligament (viembrana atlanfooccipitalis anterior) 
(Figs. 225 and 22S) is a broad membranous layer, composed of densely woven 
fibres, which passes between the anterior margin of the foramen magnum above, 
and the whole length of the upper border of the anterior arch of the atlas below. 
Laterally, it is continuous with the capsular ligaments. In the middle line in 



276 



THE ARTICULATIONS, OB JOINTS 



front it is strengthened by a strong, narrow, rounded cord, which is attached, 
above, to the basilar process of the occiput, and, below, to the tubercle on the 
anterior arch of the atlas, and which is a continuation of the anterior common 
ligament. This ligament is in relation, in front, with the Recti antici minores; 
hehiyid, with the odontoid ligaments. 

The posterior occipito-atlantal ligament (membrana atlanto-occipitalis posterior, 
posterior occipito-atloid ligament) (Figs. 226 and 228) is a very broad but thin 
membranous lamina intimately blended with the dura. It is connected, above, 
to the posterior margin of the foramen magnum; heloic, to the upper border of 
the posterior arch of the atlas. This ligament is incomplete at each side, and 
forms, with the groove in the upper surface of the posterior arch, an opening for 
the vertebral artery and suboccipital nerve. The fibrous band which arches over 
the artery and nerve sometimes becomes ossified. The ligaments are in relation, 
behind, with the Recti postici minores and Obliqui superiores; in front, with the 
dura of the vertebral canal, to which they are intimately adherent. 



POSTERIOR OC 

CIPITO-ATLANTA 

LIGAMEN 



POSTERIOR OC- 
CIPITO-ATLANTAL 
LIGAMENT 



TRANSVERSE 
PROCESS OF 
ATLAS 




Fig. 226. — Occipital bone, first and second cervical vertebree with ligaments from behind. (Spalteholz.) 

The capsular ligaments (capsulae articulares) (Fig. 227) surround the condyles 
of the occipital bone, and connect them with the articular processes of the atlas; 
they consist of thin and loose capsules, which enclose the synovial membranes 
of the articulations. 



Synovial Membranes. — There are two synovial membranes in this articulation, one lining the 
inner surface of each of the capsular ligaments. These occasional!)' communicate with that 
between the posterior surface of the odontoid process and the transverse ligament. 

Movements. — The movements permitted in this joint are flexion and extension, which give 
rise to the ordinary forward and backward nodding of the head. Slight lateral motion to one 
or the other side may also take place. When either of these actions is carried beyond a slight 
extent, the whole of the cervical portion of the spine assists in its production. Flexion \s mainly 
produced by the action of the Rectus capitis anticus major et minor and the Sternomastoid 
muscles; extension by the Rectus capitis posticus major et minor, the Obliquus superior, the 
Complexus, Splenius, and upper fibres of the Trapezius. The Recti laterales are concerned in 
the lateral movement, assisted by the Trapezius, Splenius, Complexus, and the Sternomastoid 
of the same side, all acting together. According to Cruveilhier, there is a slight amount of 
rotation in this joint. 



ARTICULATION OF THE AXIS WITH THE OCCIPITAL BONE 277 

IV. Articulation of the Axis with the Occipital Bone. 

The ligaments of this articulation are the 



Occipito-axial. 



Three Odontoid. 



To expose these ligaments the vertebral canal should be laid open by removing 
the posterior arch of the atlas, the laminae and spinous process of the axis, and 
the portion of the occipital bone behind the foramen magnum, as seen in Fig. 227. 




Fig. 227. — Occipito-axial and atlanto-axial ligaments. Posterior view, obtained by 
the vert«bri3e and the posterior part of the skull. 



^•ing the arches of 



The posterior occipito-axial ligament (membrana tectoria) (Figs. 227 and 22^) 
is situated within the vertebral canal. It is a broad, strong band, which covers 
the odontoid process and its ligaments, and appears to be a prolongation upward 
of, or a membrane due to fusion with, the posterior common ligament of the spine. 
It is attached, below, to the posterior surface of the body of the axis, and, becom- 
ing expanded as it ascends, is inserted into the basilar groove of the occipital 
bone, in front of the foramen magnum, where it becomes blended with the dura 
of the skull. 

Relations. — By its anterior surface with the transverse Hgament; by its 'posterior surface 
with the posterior common ligament. 

The lateral odontoid ligaments (ligamenta alaria) (Figs. 227 and 228) are 
strong, rounded, fibrous cords, which arise one on either side of the upper part of 
the odontoid process, and, passing obliquely upward and outward, are inserted 
into the rough depressions on the inner side of the condyles of the occipital bone. 
In the triangular interval left between these ligaments another strong fibrous 



278 



THE ARTICULATIONS, OR JOINTS 



cord, the middle odontoid ligament (ligavientum apicis dentis), may be seen, which 
passes ahnost perpendicularly from the apex of the odontoid process to the 
anterior margin of the foramen magnum, being intimately blended with the 
deep portion of the anterior occipito-atlantal ligament and upper fasciculus of 
the transverse ligament of the atlas. 

Movements. — The odontoid ligaments serve to limit tlie extent to which rotation of the 
cranium may be carried; hence, they have received the name of check ligaments. 

In addition to these ligaments, which connect the atlas and axis to the skull, the ligamentum 
nuchae must be regarded as one of the ligaments by which the vertebral column is connected with 
the cranium. It is described on page 272. 



L-VE- OF POSTERIOR COMMON 
Lf T L PARATED FROM THE 
LH OH OCCrPITO-AXIAL LIGAMENT 



ANTERIOR OCCIFITO ■ Js ^^Li 
ITLANTAL LIGA^ ENT ' (v^ V 




ANTERIOR COM 



Fig. 228.— Median sagittal section through the occipital bone and first three cervical vertebrae with ligaments. 

(Spalteholz). 

Applied Anatomy.— The ligaments which unite the component parts of the vertebrre together 
are.so strong, and these bones are so interlocked by the arrangement of their articulating processes, 
that dislocation is very uncommon, and, indeed, "unless accompanied hy fracture, seldom occurs, 
except in the upper part of the neck. Dislocation of the occiput from the atlas has only been 
recorded m one or two cases; but dislocation of the atlas from the axis, with rupture of the trans- 
verse ligament, is much more common; it is the mode in which death is produced in some cases 
ot execution by hanging. In the lower part of the neck— that is, below the third cervical vertebra 
—dislocation unattended by fracture occasionally takes place. 



TEMPOBOMANDIB ULAR ARTICULATION 



279 



V. Temporomandibular Articiilation (Articulatio Mandibularis) . 

This is a ginglymo-arthrodial joint; the parts entering into its formation on 
each side are, above, the anterior part of the glenoid cavity of the temporal bone 
and the eminentia articularis; and, below, the condyle of the mandible. The 
ligaments are the following: 



External Lateral. 
Internal Lateral. 



Articular Disk 



Stylomandibular. 
Capsular. 



The external lateral ligament {ligamenium temporomaitdibulare) (Fig. 229) 
is a short, thin, and narrow fasciculus, attached, above, to the outer surface of 
the zygoma and to the tubercle on its lower border; beloiv, to the outer border of 
the neck and to the tubercle at the outer extremity of the condyle of the mandible. 
It is broader above than below; its fibres are placed parallel to one another, 




ss»m\ ^ ^^^^ Temporal bone. k\ , ,A 





Fig. 229. — Tempoi 



and directed obliquely downward and backward. Externally, it is covered by 
the parotid gland and by the integument. Internally it is in relation with the 
capsular ligament, of which it is an accessory band, and from which it is not 
separable. 

The internal lateral ligament (licfamentum sphenomandibulare) (Fig. 230) is 
.a flat, thin band which is attached above to the spine of the sphenoid bone, and, 
becoming broader as it descends, is inserted into the margin of the dental foramen 
and the portion of bone, the lingula, which overhangs the foramen in front. 
This ligament is not a true articular ligament, but is an accessory band, contrib- 
uted to the capsule by the deep cervical fascia. Its outer surface is in relation, 
above, with the External pterygoid muscle; lower down it is separated from the 
neck of the condyle by the internal maxillary artery; and still more inferiorly, 
the inferior dental vessels and nerve separate it from the ramus of the mandible. 
The inner surface is in relation with the Internal pterygoid. 



280 



THE ARTICULATIONS, OB JOINTS 




Fig. 230. — Temporomandibular articulation. Internal 



The stylomandibular ligament Qigamentum stylomandibulare) (Fig. 230) is a 
specialized band of the cervical fascia, which extends from near the apex of the 
styloid process of the temporal bone to the angle and posterior border of the 
ramus of the mandible, between the Masseter and Internal pterygoid muscles. 
This ligament separates the parotid from the submaxillary gland, and has 

attached to its inner side part of 
the fibres of origin of the Stylo- 
glossus muscle. Although usually 
classed among the ligaments of 
the mandible, it can be considered 
only as an accessory to the articu- 
lation. 

The capsular ligament {cap- 
sula articularis) (Figs. 229 and 
230) forms a thin and loose cap- 
sule, passing from the circum- 
ference of the glenoid cavity and 
the articular surface immediately 
in front to the upper margin of 
the articular disk, and from the 
lower margin of the articular disk 
to the neck of the condyle of the 
mandible. It consists of very 
thin fibres, and is complete. It 
forms two joint cavities, distinct 
from each other, and separated 
by the articular disk. So thin is 
it that it is hardly to be considered as a distinct ligament; it is thickest at the 
back part, and thinnest on the inner side of the articulation.' 

The articular meniscus (discus articularis) (Fig. 231) is a thin plate of an oval 
form, placed horizontally between the condyle of the mandible and the glenoid 
cavity. Its upper surface is con- 
cavo-convex from before backward, 
and a little convex transversely, to 
accommodate itself to the form of 
the glenoid cavity. . Its under sur- 
face, where it is in contact with the 
condyle, is concave. Its circumfer- 
ence is connected to the capsular 
ligament, and in front to the tendon 
of the External pterygoid muscle. 
It is thicker at its circumference, 
especially behind, than at its centre. 
The fibres of which it is composed 
have a concentric arrangement, more 
apparent at the circumference than 
at the centre. Its surfaces are 
smooth. It divides the joint into two cavities, each of which is furnished with a 
separate synovial membrane reflected from the capsular ligament. 

Synovial Membranes (Fig. 231). — The synovial membranes, tivo in number, are placed, 
one above, and the other below, the articular disk. The upper one, the larger and looser of the 
two, is continued from the margin of the cartilage covering the glenoid cavity and eminentia 

' Sir G. Humphry describes the internal portion of the capsular ligament separately as the short internal 
lateral ligament; and it certainly seems as deserving of a separate description as is the external lateral ligament. 




THE TEMPOROMANDIBULAR ARTICULATION 281 

articularis on to the upper surface of the articular disk. The lower one passes from the under 
surface of the articular disk to the neck of the condyle of the mandible, being prolonged down- 
ward a little farther behind than in front. The articular disk is sometimes perforated in its 
centre; the two synovial sacs then communicate with each other. 

The nerves of this joint are derived from the auriculotemporal and masseteric branches 
of the inferior maxillary. The arteries are derived from the temporal branch of the external 
carotid. 

Movements. — The movements possible in this articulation are very extensive. Thus, the 
mandible may be depressed or elevated, or it may be carried forward or backward. It must be 
borne in mind that there are two distinct joints in this articulation — that is to say, one between 
the condyle of the mandible and the articular disk, and another between the disk and the glenoid 
fossa; when the mandible is depressed, as in o])e'ning the mouth, the movements which take place 
in these two joints are not the same. In the lower compartment, that between the condyle and 
the articular disk, the movement is of a ginglymoid or hinge-like character, the condyle rotating 
on a transverse axis on the articular disk; while in the upper compartment the movement is of 
a gliding character, the articular disk, together with the condyle, gliding forward on to the 
eminentia articularis. These two movements take place simultaneously — the condyle and 
articular disk move forward on the eminence, and at the same time the condyle revolves on 
the articular disk. In the opposite movement of shutting the mouth the reverse action takes 
place; the articular disk glides back, carrying the condyle with it, and this at the same time 
revolves back to its former position. When the mandible is carried horizontally forward, as 
in protruding the lower incisors in front of the upper, the movement takes place principally 
in the upper compartment of the joint — the articular disk, carrying with it the condj'le, glides 
forward on the glenoid fossa. This is because this movement is mainly effected by the External 
pterygoid muscles, which are inserted into both condyle and articular disk. The grinding or 
chewing movement is produced by the alternate movement of one condyle, with its disk, for- 
, ward and backward, while the other condyle moves simultaneously in the opposite direction; 
at the same time the condyle undergoes a vertical rotation on its own axis on the disk in the 
lower compartment. One condyle advances and rotates, the other condyle recedes and rotates, 
in alternate succession. 

The mandible is depressed by its own weight, assisted by the Platysma, the Digastric, the 
Mylohyoid, and the Geniohyoid muscles. It is elevated by the anterior part of the Temporal, 
Masseter, and Internal pterygoid muscles. It is drawn forward by the simultaneous action of 
the External pterygoid and the superficial fibres of the Masseter; and it is drawn backward by 
the deep fibres of the Masseter and the posterior fibres of the Temporal muscles. The grinding 
movement is caused by the alternate action of the two External pterygoids. 

Surface Form. — The temporomandibular articulation is quite superficial, situated below the 
base of the zygoma, in front of the tragus and external auditory meatus, and behind the posterior 
border of the upper part of the Masseter muscle. Its exact position can be at once ascertained 
by feeling for the condyle of the mandible, the working of which can be distinctly felt in the 
movements of the mandilile in opening and shutting the mouth. When the mouth is opened 
wide, the condyle advances out of the glenoid fossa on to the eminentia articularis, and a depres- 
sion is felt in the situation of the joint. 

Applied Anatomy. — Genuine dislocation of the mandible is almost always forward. Croker, 
King, and Theim, however, have reported posterior displacement. Dislocation is caused by vio- 
lence or muscular action. When the mouth is open, the condyle is situated on the eminentia 
articularis, and any sudden violence, or even a sudden muscular spasm, as during a convulsive 
yawn, may displace the condyle forward into the zygomatic fossa. The displacement may be 
unilateral or bilateral, according as one or both of the condyles is displaced. The latter of the 
two is the more common. The articular disk adheres to the condyle until it passes over the 
eminentia articularis, but at this point remains behind. 

Sir Astley Cooper described a condition which he termed "subluxation." It occurs princi- 
pally in delicate women, and is belived by some to be due to the relaxation of the ligaments, 
permitting too free movement of the bone. Others believe it is due to displacement of the articular 
disk. Still others attribute the symptoms to gouty or rheumatic changes in the joint. In close 
relation to the condyle of the mandible is the external auditory meatus and the tympanum; 
any force, therefore, applied to the bone is liable to be attended with damage to these parts, or 
inflammation in the joint may extend to the ear, or, on the other hand, inflammation of the middle 
ear may involve the articulation and cause its destruction, thus leading to ankylosis of the joint. 
In children, arthritis of this joint may follow the exanthemata, and in adults it occurs as the 
result of some constitutional conditions, as rheumatism or gout. The temporomandibular 
joint is also occasionally the seat of osteoarthritis, leading to great suffering during efforts of mas- 
tication. A peculiar affection sometimes attacks the neck and condyle of the mandible, consisting 
in hypertrophy and elongation of these parts and consequent protrusion of the chin to the opposite 
side. 



282 



THE ARTICULATIONS, OR JOINTS 



VI. Articulations of the Ribs with the Vertebrae or the Costovertebral 
Articulations (Articulationes Costovertebrales). 

The articulations of the ribs with the vertebral column may be divided into 
two sets: (1) Those which connect the heads of the ribs with the bodies of the 
vertebrae — costocentral. (2) Those which connect the necks and tubercles of the 
ribs with the transverse processes — costotransverse. 



1. Costocentral Articulations (Articulationes Capitulorum) 
(Figs. 232 and 233). 

These constitute a series of arthrodial joints, formed by the articulation of the 
heads of the ribs with the cavities on the contiguous margins of the bodies of the 




Fig. 232.— Vertebral column 



(Spalteholz.) 



thoracic vertebras and the intervertebral substance between them, except in the 
case of the first, tenth, eleventh, and twelfth ribs, where the cavity is formed 
by a single vertebra. The bones are connected by the following ligaments: 

Anterior Costovertebral or Stellate. 
Capsular. Intra-articular 

The anterior costovertebral or stellate ligament (ligamentum capituli costae 
radiatum) (Figs. 232 and 235) connects the anterior part of the head of each 
rib with the sides of the bodies of two vertebrae and the intervertebral disk 
between them. It consists of three flat bundles of ligamentous fibres, which are 
attached to the anterior part of the head of the rib, just beyond the articular 



ARTICULATIONS OF THE BIBS WITH THE VEBTEBBJE 283 

surface. The superior fibres pass upward to be connected with the body of 
the vertebra above; the inferior one descends to the body of the vertebra below; 
and the middle one, the smallest and least distinct, passes horizontally inward, 
to be attached to the intervertebral substance. 

On the first rib, which articulates with a single vertebra, this ligament does 
not present a distinct division into three fasciculi; its fibres, however, radiate, 
and are attached to the body of the last cervical vertebra, as well as to the body 
of the vertebra with which the rib articulates. In the tenth, eleventh, and twelfth 
ribs also, which likewise articulate with a single vertebra, the division does not 
exist; but the fibres of the ligament in each case radiate and are connected with 
the vertebra above, as well as that with which the ribs articulate. 

Relations. — In front, with the thoracic ganglia of the sympathetic, the pleura, and, on the 
right side, with the vena azygos major; behind, with the interarticular ligament and synovial 
membranes. 



The capsular ligament (capsula articularis) is a thin and loose ligamentous 
bag, which surrounds the joint between the head of the rib and the articular 
cavity formed by the inter- 
vertebral disk and the ad- 
jacent vertebra. It is very 
thin, firmly connected with 
the anterior ligament, and 
most distinct at the upper 
and lower parts of the 
articulation. Behind, some 
of its fibres pass through 
the intervertebral foramen 
to the back of the inter- 
vertebral disk. This is the 
}\om.o\ogueoH\\e.liga'mentum 
conjugale of some mammals, 
which unites the heads of 
opposite ribs 'across the 
back of the intervertebral 
disk. 

The intra-articular liga- 
ment (Jigamentum capifidi 
costae interarticidare) (Figs. 
23.3 and 234) is situated in 
the interior of the joint. It 
consists of a short band of 

fibres, flattened from above downward, attached by one extremity to the sharp 
crest which separates the two articular facets on the head of the rib, and by the 
other to the intervertebral disk. It divides the joint into two cavities, which 
have no communication with each other. For the first, tenth, eleventh, and 
twelfth ribs the intra-articular ligament does not exist; consequently there is 
but one synovial membrane. 

Synovial Membranes (Figs. 233 and 234). — There are two syno\'iaI membranes in each of 
the articulations in which there is an intra-articular ligament, one on each side of this structure. 




284 



THE ARTICULATIONS, OB JOINTS 



2. Costotransverse Articulations (Articulationes Costotransversariae) 

(Fig. 234). 

The articular portion of the tubercle of the rib and adjacent transverse process 
form an arthrodial joint. 

For the eleventh and twelfth rihs this articulation is wanting. 
The ligaments connecting these parts are the 



Anterior or Superior Costotransverse. 
Middle Costotransverse (Interosseous). 



Posterior Costotransverse. 
Capsular. 



The anterior or superior ligament (ligamentum costotransversarium anterius) 
(Figs. 234 and 235) consists of two sets of fibres; the one (anterior) is attached 
below to the sharp crest on the upper border of the neck of each rib, and passes 




Fig. 234. — Costotransverse articulation. Seen from above. 

obliquely upward and outward to the lower border of the transverse process 
immediately above; the other (posterior) is attached below to the neck of the rib, 
and passes upward and inward to the base of the transverse process and outer 
border of the lower articular process of the vertebra above. 

The first rib has no anterior costotransverse ligament. For the twelfth rib the 
ligament is absent or is a mere vestige. 

Relations. — This ligament is in relation, in front, with the intercostal vessels and nerves; 
behind, with the Longissimus dorsi muscle. Its internal border is thickened and free, and bounds 
an aperture through which pass the posterior branches of the intercostal vessels and nerves. Its 
external border is continuous with a thin aponeurosis which covers the External intercostal 
muscle. 

The middle costotransverse or interosseous ligament (ligamentum colHcostae} 
(Fig. 234) consists of short but strong fibres which pass between the rough surface 
on the posterior part of the neck of each rib and the anterior surface of the ad- 
jacent transverse process. In order to fully expose this ligament, a horizontal 



VERSE LIG 
INTER! 
VERSE LIGAMENT 



ARTICULATIONS OF THE BIBS WITH THE VERTEBRA 285 

section should be made across the transverse process and corresponding part 
of the rib; or the rib may be forcibly separated from the transverse process and 
the fibres of tlie ligament put on the stretch. 

For the eleventh and twelfth ribs this ligament is quite rudimentary or wanting. 

The posterior costotransverse ligament (ligamentum costotransversarmm pos- 
ierius) (Fig. 234) is a short but thick and strong fasciculus which passes obliquely 
from the summit of the transverse process to the rough nonarticular portion of 
the tubercle of the rib. 

This ligament is shorter ^\o. 

and more oblique in the 
upper than in the lower 
ribs. Those correspon- 
ding to the superior ribs 
ascend, while those of 
the inferior ribs descend 
slightly. 

For the eleventh and 
twelfth ribs this ligament 
is M-anting. 

The capsular liga- 
ment (capsula artic'ular- 
is) is a thin, membranous 
sac attached to the cir- 
cimiference of the articu- 
lar surfaces, and enclos- 
inga syno\-ial membrane. 

For the eleventh and 
twelfth ribs this ligament 
is absent. 

Movements.~The heads 
of the ribs are so closely 
connected to the bodies of 
the vertebrae by the stellate 
and intra-articular hgaments, 
and the necks and tubercles 

of the ribs to the transverse Fig. 235. — Ribs and corresponding -vertebra; with ligaments, 

processes, that only a slight ^^^ "sht. (Spaltehoh.) 

gliding movement of the ar- 
ticular surfaces on each other can take place in these articulations. The result of this gliding 
movement with respect to the six upper ribs consists in, an elevation of the front and middle 
portion of the rib with a consequent enlargement of the antero-posterior diameter of the thorax, 
the hinder part being prevented from performing any upward movement by its close connection 
with the vertebral column. In this gliding movement the rib rotates on an axis corresponding 
to a line drawn through the two articulations, costocentral and costotransverse, which the rib 
forms with the vertebral column. None of the ribs lie in a truly horizoiKal plane; they are all 
directed more or less obliquely, so that their anterior extremities lie at a lower level than their 
posterior; this obliquity increases from the first to the seventh, and then again decreases. If we 
examine any one rib — say that in which there is the greatest obliquity — we shall see that it is 
obvious that as its sternal extremity is carried upward it must also be thrown forward; so that 
the rib may be regarded as a radius moving on the vertebral joint as a centre, and causing the 
.sternal attachment to describe an arc of a circle in the vertical plane of the body. Since all the 
ribs are oblique and connected in front to the sternum by the flexible costal cartilages, they 
must have a tendency to thrust the sternum forward, and so increase the antero-posterior diameter 
of the thorax. With respect to the seventh, eighth, ninth, and tenth ribs, each one, besides rotating 
in a similar manner to the upper six, also rotates on an axis corresponding with a line drawn from 
the head of the rib to the sternum. By this movement an elevation of the middle portion of the 
rib takes place, and consequently an increase in the transverse diameter of the thorax. For the 
ribs not only slant downward and forward from their vertebral attachment, but they are also 
oblique in relation to their transverse plane — that is to say, their middle is at a lower level than 




INFERIOR AHTIC 
ULAfl PROCESS 



286 



THE ARTICULATIONS, OB JOINTS 



either their vertebral or sternal extremities. It results from this that when the ribs are raised, the 
central portion is thrust outward, somewhat after the fashion in which the handle of a bucket is 

thrust away from the side when raised to 
a horizontal position, and the lateral 
I ijl diameter of the thorax is increased (see 

Fig. 236). The mobility of the diflerent 
ribs varies greatly. The first rib is more 
fixed than the others, on account of the 
weight of the upper extremity and the 
strain of the ribs beneath; but on the 
freshly dissected thorax it moves as 
freely as the others. From the same 
causes the movement of the second rib is 
also not very extensive. In the other 
ribs this mobility increases successively 
down to the last two, which are very 
movable. The ribs are generally more 
movable in the female than in the male. 



VII. Costosternal Articulations 
(Articulationes Sternocostales) 

(Fig. 237). 




^ Fig. 236. — I)i:im:njis .showing the axis of rotation of the 
ribs in the moveiiieiiU ut respiration. The one axi.s of rota- 
tion corresponds with the Une drawn through the two articula- 
tions which the rib forms with the vertebral column (a, 6), and 
the other with a line drawn from the head of the rib to the 
sternum (A, B). (From Kirke's Handbook of Physiology.) 



The articulations of the carti- 
lages of the true ribs with the 
sternum are arthrodial joints, with 
the exception of the first, in which 
the cartilage is almost always 
directly united with the sternum, 
and which must therefore be re- 
garded as a synarthrodial articu- 
lation. Tlae ligaments connecting 
them are the 

Anterior Chondrosternal. 

Capsular. 

Posterior Chondrosternal. 

Intra-articular Chondrosternal. 

Chondroxiphoid. 



The anterior chondrosternal ligament (liganientum sternocostale radiatum) (Fig. 
237) is a broad and thin membranous band that radiates from the front of the inner 
extremity of the cartilages of the' true ribs to the anterior surface of the sternum. 
It is composed of fasciculi which pass in different directions. The superior 
fasciculi ascend obliquely, the inferior fasciculi pass obliquely downward, and 
the middle fasciculi pass horizontally. The superficial fibres of this ligament 
are the longest; they intermingle with the fibres of the ligaments above and 
below them, with those of the opposite side, and with the tendinous fibres of 
origin of the Pectoralis major, forming a thick fibrous membrane which covers 
the surface of the sternum (inembraiia sterni). This is more distinct at the 
lower than at the upper part. 

The capsular ligament (capsida articidaris) surrounds the joint formed between 
the cartilage of a true rib and the sternum. It is very thin, intimately blended 
with the anterior and posterior ligaments, and strengthened at the upper and 
lower part of the articulation by a few fibres which pass from the cartilage to 
the side of the sternum. These ligaments protect the synovial membranes. 

The posterior chondrosternal or sternocostal ligament (ligamentum sterno- 
costale radiatum), less thick and distinct than the anterior, is composed of fibres 



COSTOSTERNAL ARTICULA TI0N8 



287 



which radiate from the posterior surface of the sternal end of the cartilages of 
the true ribs to the posterior surface of the sternum, becoming blended with the 
periosteum. 

The intra-articular chondrosternal ligament {ligamentum sternocostale inier- 
articulare) (Fig. 237) is found between the second costal cartilage and the sternum. 
The cartilage of the second rib is connected with the sternum by means of an 




Fig. 237. — Sternum and ribs with ligaments, from in front. In the right half of the figure the most anterior 
layer has been removed and the joint cavities have been opened; the parts are separated somewhat from one 
another on the left side. (Spalteholz.) 

intra-articular ligament attached by one extremity to the cartilage of the second 
rib, and by the other extremity to the cartilage which unites the first and second 
pieces of the sternum. This articulation is provided with two synovial membranes. 
The cartilage of the third rib is also occasionally connected with the sternum 
by means of an intra-articular ligament which is attached by one extremity to 
the cartilage of the third rib, and by the other extremity to the sternum. This 



288 THE ARTICULATIONS, OB JOINTS 

articulation may be provided with two synovial membranes. In the other joints 
intra-articular ligaments may exist, but they rarely completely divide the joint 
into two cavities. 

The anterior chondroxiphoid ligament (ligamentum costoxiphoideum anterius) 
(Fig. 237) is a band of ligamentous fibres which connects the anterior surface 
of the seventh costal cartilage, and occasionally also that of the sixth, to the 
anterior surface of the ensiform cartilage. It varies in length and breadth in 
different subjects. A similar band of fibres on the posterior surface, though 
less thick and distinct, may be demonstrated. It is spoken of as the posterior 
chondroxiphoid ligament. 

Synovial Membranes (Fig. 2.37). — There is no synovial membrane between the first costal 
cartilage and the sternum, as this cartilage is directly continuous with the manubrium. There are 
tioo synovial membranes, both in the articulation of the second and third costal cartilages to the 
sternum. There is generally one synovial membrane in each of the joints between the fourth, 
fifth, sixth, and seventh costal cartilages to the sternum; but it is sometimes absent in the sixth 
and seventh chondrosternal joints. Thus, there are usually eiyht synovial cavities on each side 
in the articulations between the costal cartilages of the true ribs and the sternum. After middle 
life the articular surfaces lose their polish, become roughened, and the synovial membranes 
appear to be wanting. In old age the articulations do not exist, the cartilages of most of the 
ribs becoming continuous with the sternum. 

Movements. — The movements which are permitted in the chondrosternal articulations are 
limited to elevation and depression, and these only to a slight extent. 

Articulations of the Cartilages of the Ribs with Each Other {articulationes 
interchondrales) (Fig. 237). — The contiguous borders of the sixth, seventh, and 
eighth, and sometimes the ninth and tenth, costal cartilages articulate with each 
other by small, smooth, oblong-shaped facets. Each articulation is enclosed in 
a thin capsular ligament lined by synovial membrane, and strengthened externally 
and internally by ligamentous fibres, external and internal interchondral ligaments 
(ligamenta intercostalia externa et interna), which pass from one cartilage to the 
other. Sometimes the fifth costal cartilage, more rarely that of the ninth, articu- 
lates, by its lower border, with the adjoining cartilage by a small oval facet; 
more frequently they are connected by a few ligamentous fibres. Occasionally 
the articular surfaces above mentioned are wanting. 

Articulations of the Ribs with their Cartilages (Fig. 237).— The outer 
extremity of each costal cartilage is received into a depression in the sternal 
ends of the ribs, and the two are held together by the periosteum. There is no 
real joint. Occasionally a synovial membrane exists between the first rib and 
the corresponding cartilage. 

VIII. Articulations of the Sternum (Fig. 237) 

The first piece of the sternum is united to the second either by an amphi- 
arthrodial joint — a single piece of true fibrocartilage uniting the segments — or by 
a diarthrodial joint, in which each bone is clothed with a distinct lamina of hyaline 
cartilage, adherent on one side, free and lined with synovial membrane on the 
other. In the latter case the cartilage covering the gladiolus is continued without 
interruption on to the cartilages of the second ribs. The two segments are 
further connected by an 

Anterior Intersternal I^igament. Posterior Intersternal Ligament. 

The anterior intersternal ligament consists of a lajer of fibres, having a longi- 
tudinal direction ; it blends with the fibres of the anterior chondrosternal liga- 
ments on both sides, and with the tendinous fibres of origin of the Pectoralis 



ARTICULATION OF VERTEBRAL COLUMN WITH THE PELVIS 289 

major muscle. This ligament is rough, irregular, and much thicker below than 
above. 

The posterior intersternal ligament is disposed in a somewhat similar manner 
on the posterior surface of the articulation. 



IX. Articulation of the Vertebral Column with the Pelvis. 

The ligaments connecting the last lumbar vertebra with the sacrum are similar 
to those which connect the segments of the vertebral column with each other — viz. : 
(1) The continuation downward of the anterior and posterior common liga- 
ments. (2) The intervertebral substance connecting the flattened oval surfaces 
of the two bones and forming an amphiarthrodial joint. (.3) Ligamenta subflava, 
connecting the arch of the last lumbar vertebra with the posterior border of the 
sacral canal. (4) Capsular ligaments connecting the articulating processes and 
forming a double arthrodia. (5) Inter- and supraspinous ligaments. 




Occasional aperture of 
communication with 
Bursa 0/ psoas and iliacus. 



Femur. 

Fig. 238. — Articulations of the pelvis and hip. Anterior ' 

The two proper ligaments connecting the pelvis with the vertebral column are 
the lumbosacral and iliolumbar. 

The lumbosacral ligament (Fig. 2.38) is a short, thick, triangular fasciculus, 
which is connected above to the lower and front part of the transverse process 
of the last lumbar vertebra; it passes obliquely outward and is attached below 
to the lateral surface of the base of the sacrum. It is closely blended with the 
anterior sacroiliac and the iliolumbar ligaments, and is to be regarded as a portion 
■ of the iliolumbar ligament. This ligament is in relation, in frojit, with the Psoas 
muscle. The internal border of the lumbosacral ligament margins the foramen 
of the last lumbar nerve. 



290 THE ARTICULATIONS, OB JOINTS 

The iliolumbar ligament (Hgamentum iliolumhale) (Fig. 238) passes horizontally 
outward from the apex of the transverse process of the last lumbar vertebra to 
the crest of the ilium immediately in front of the sacroiliac articulation. It 
is of a triangular form, thick and narrovsf internally, broad and thinner externally. 
It is in relation, in front, vi'ith the Psoas muscle; behind, with the muscles occupy- 
ing the vertebral groove; above, with the Quadratus lumborum. It blends in 
places with the lumbosacral ligament, and its crescentic inner margin marks 
the limit of the foramen for the fourth limibar nerve. These ligaments are thick 
prolongations from the anterior layer of the lumbar fascia. 

X. Articulations of the Pelvis. 

The ligaments connecting the bones of the pelvis with each other may be 
divided into four groups: (1) Those connecting the sacrum and ilium. (2) Those 
passing between the sacrum and ischium. (3) Those connecting the sacrum and 
coccyx. (4) Those between the tv/o pubic bones. 

1. Articulation of the Sacrum and Ilium (Articulatio Sacroiliaca). 

The sacroiliac articulation is an amphiarthrodial joint, formed between the 
lateral surfaces of the sacrum and ilium. The anterior or auricular portion of 
each articular surface is covered with a thin plate of hyaline cartilage, thicker 
on the sacrum than on the ilium. These ai'e in close contact with each other, 
and to a certain extent united together by irregular patches of softer fibro- 
cartilage, and at their upper and posterior part by fine fibres of interosseous 
fibrous tissue. Throughout a considerable part of their extent, especially in 
advanced life, they are not connected together, but are separated "by a space 
containing a synovial-like fluid, and hence the joint presents the characters of 
a diarthrosis. 

The ligaments connecting these surfaces are the 

Anterior Sacroiliac. Posterior Sacroiliac. 

The anterior sacroiliac ligament (Ugamenta sacroiliaca anteriora) (Fig. 238) 
consists of numerous thin bands which connect the anterior surfaces of the 
sacrum and ilium. 

The posterior sacroiliac ligament Qigamentum sacroUiacum posterius) (Fig. 239) 
is a strong ligament, situated in a deep depression between the sacrum and ilium 
behind, and forming the "chief bond of connection between those bones. It 
consists of numerous strong fasciculi which pass between the bones in various 
directions. The upper part of the ligament, the short sacroiliac {Hgamentum 
sacroiliacuni posterius breve) is nearly horizontal in direction and passes from 
the first and second transverse tubercles on the posterior surface of the sacrum 
to the rough, uneven surface at the posterior part of the inner surface of the 
ilium. The lower part (Hgamentum sacroUiacum posterius longum), oblique in 
direction, is attached by one extremity to the third transverse tubercle on the 
posterior surface of the sacrum, and by the other to the posterior superior spine 
of the ilium; it is sometimes called the oblique sacroiliac ligament. 

Surface Form. — The position of the sacroiliac joint is indicated by the posterior superior 
spine of the ilium. This process is immediately behind the centre of the articulation. 



ARTICULATIONS OF THE PELVIS 



291 



2. Ligaments Passing between the Sacrum and Ischium (Fig. 239). 

The Great Sacrosciatic (Posterior). 
The Small Sacrosciatic (Anterior). 

The great or posterior sacrosciatic ligament {Ugamentum sacroiuberosum) (Figs. 
239 and 240) is situated at the lower and back part of the pelvis. It is flat, and 
triangular in form; narrower in the middle than at the extremities; attached 
by its broad base to the posterior inferior spine of the ilium, to the fourth and 
fifth transverse tubercles of the sacrum, and to the lower part of the lateral margin 
of that bone and the coccyx. Passing obliquely downward, outward, and for- 




^ Femm 

Fig. 239. — .Articulations of pelvis and hip. Posterior Mew 

ward, it becomes narrow and thick, and at its insertion into the inner margin 
of the tuberosity of the ischium it increases in breadth, and is prolonged forward 
along the inner margin of the ramus, forming what is known as the falciform 
process of the great sacrosciatic ligament {processus falciformis) . The free concave 
edge of this prolongation has attached to it the obturator fascia, with which it 
forms a kind of groove, protecting the internal pudic vessels and nerve. One 
of its surfaces is turned toward the perineum, the other toward the Obturator 
internus muscle. 

Relations. — The superficial surface of this ligament gives origin, by its whole extent, to fibres 
of the Gluteus ma.xiraus muscle. Its deep surface is united to the lesser sacrosciatic ligament. 
Its external border forms, above, the posterior boundary of the great sacrosciatic foramen, and, 
below, the posterior boundary of the lesser sacrosciatic foramen. Its loioer border forms part 
of the boundary of the perineum. It is pierced by the coccygeal branch of the sciatic artery 
and the coccygeal nerve. 



292 



THE ARTICULATIONS, OB JOINTS 



The small or anterior sacrosciatic ligament {ligamentum sacrospinosuTri) (Figs. 
239 and 240), much shorter and smaller than the preceding, is thin, triangular 
in form, attached by its apex to the spine of the ischium, and internally, by its 
broad base, to the lateral margin of the sacrum and coccyx, anterior to the attacli- 
ment of the great sacrosciatic ligament, with wliich its fibres a're intermingled. 




-ANT. SACI 


aOILlAC 


LIGAMENT. 


-GREAT SA 


CRO- 


SCIATIC 


LIGA- 


MENT. 




.SMALL SA< 


CRO- 


SCIATIC 


LIGA- 


MENT. 




.GREAT SA 


CRO- 


SCIATIC 


LIGA' 


MENT. 





Obtu. 
membrane. 



Fig. 240. — Side view of pelvis, showing the greater and lesser sacrosciatic ligaments. 



Relations. — Its deep surface is in relation with the Cotcygeus muscle; its superficial surface 
is covered by the great sacrosciatic ligament and crossed by the internal pudic vessels and 
nerve. Its superior harder forms the lower boundary of the great sacrosciatic foramen; its 
inferior border, part of the lesser sacrosciatic foramen. 

These two ligaments convert the sacrosciatic notches into foramina. The superior or great 
sacrosciatic foramen (foramen ischiadicmn majiis) (Figs. 239 and 240) is bounded, in front and 
above, by the posterior border of the os innominatum;fcp/«"?!fi, by the great sacrosciatic ligament; 
and below, by the lesser sacrosciatic ligament. It is partially filled in the recent state by the 
Pyriformis muscle, which passes through it. Above this muscle the gluteal vessels and superior 
gluteal nerve emerge from the pelvis, and, below it, the sciatic vessels and nerves, the internal 
pudic vessels and nerve, the inferior gluteal nerve, and the nerves to the Obturator internus and 
Quadratus femoris. The inferior or lesser sacrosciatic foramen (foramen ischiadicum minus) 
(Figs. 239 and 240) is bounded, in front, by the tuber ischii; above, by the spine and lesser sacro- 
sciatic ligament; behind, by the greater sacrosciatic ligament. It transmits the tendon of the 
Obturator internus muscle, its nerve, and the internal pudic vessels and nerve. 



3. Articulation of the Sacrum and Coccyx (Symphysis Sacrococcygea). 

This articulation is an amphiarthrodial joint, formed between the oval surface 
at the apex of the sacrum and the base of the coccyx. It is analogous to the 
joints between the bodies of the vertebrae. The ligaments are the 



Anterior Sacrococcygeal. 
Posterior Sacrococcygeal. 



Lateral Sacrococcygeal. 
Interposed Fibrocartilage. 



ABTICULATIONS OF THE PELVIS 



293 



The anterior sacrococcygeal ligament {llgamentum sacrococcygemn anierius) 
consists of a few irre<j;ular fibres which descend from the anterior surface of the 
sacrum to the front of the coccyx, becoming blended with the periosteum. It 
is a continuation of tiie anterior common ligament. 

The posterior sacrococcygeal ligament [ligameufum sacmcoccygeum poaferim) 
(Fig. 241) is divided into two portions, tiie deep and the superficial. Tlie deep 
portion (Ikjamcidum sacrococcygcum posterius profuiidum), which is a continua- 
tion of the posterior common ligament, is a flat band of a pearly tint, which arises 
from the margin of the lower orifice of the sacral canal, and descends to be inserted 
into the posterior surface of the coccyx. This ligament completes the lower 
and back part of the sacral canal. Its superficial fibres are much longer than 
the more deeply seated. This ligament is in relation, behind, with the Gluteus 
maximus. The superficial portion (ligamentum sacrococcygeiivi posferius super- 
ficiale) is composed of longitudinal fibrous bands which extend from the lower 
portion of the middle sacral ridge to the posterior surface of the coccyx and 
closes partly the sacral hiatus, and of fibrous bands which extend from the sacral 
cornua to the coccygeal cornua. A portion of this ligament corresponds to the 
ligamenta subflava and the balance to the capsular ligament. 




EX OF SACRUM 

LATERAL SACBO- 

CCYGEAL LIGAMENT 
PERFICIAL PORTION OF POST 
CROCOCCYGEAL LIGAMENT 
EF PORTION OF POSTERIOR 

SACROCOCCYGEAL LIGAMENT 



Fig. 241. — Ligaments between the 



and the coccyx. (Spalteholz.) 



A lateral sacrococcygeal or intertransverse ligament (Fig. 241) connects the 
trans\'erse process of the coccyx to the lower lateral angle of the sacrum on each 
side. 

A fibrocartilage or articular disk is interposed between the contiguous surfaces 
of the sacrum and coccyx; it diti'ers from that interposed between the bodies of 
the vertebrae in being thinner, and its central part firmer in texture. It is some- 
what thicker in front and behind than at the sides. Occasionally, a synovial 
membrane is found and the coccyx is freely movable. This is especially the case 
during pregnancy. 

The different segments of the coccjnc are connected by an extension downward 
of the anterior and posterior sacrococcygeal ligaments, a thin annular articular 
disk being interposed between each of the bones. In the adult male all the 
pieces become ossified, but in the female this does not commonly occur until a 
later period of life. The separate segments of the coccyx are first united, and at 
a more advanced age the joint between the sacrum and coccyx is obliterated. 



294 



THE ARTICULATIONS, OB JOINTS 



Movements.— The movements which take place between the sacrum and coccyx, and between 
the different pieces of the latter bone, are forward and backward, and are very limited. Their 
extent increases during pregnancy. 



Interpubic dish 
Cavity at uppe 
and back pa} t 



4 Articulation of the Pubic Bones (Symphysis Ossioi Pubis) 
(Figs. 238, 242). 

The articulation between the pubic bones is an amphiarthrodial joint, formed 
by the apposition of the two oval articular surfaces of the pubic bones. The 
ligaments of this articulation are the 

Anterior Pubic. Superior Pubic. 

Posterior Pubic. Inferior Pubic. 

Interpubic Disk. 

The anterior pubic Ugament (Fig. 238) consists of several superimposed layers 
which pass across the front of the articulation. The superficial fibres pass ob- 
liquely from one bone to the other. 
Hyaline cartiiaiie coveHnri bone. decussating and forming an interlace- 

ment with the fibres of the aponeurosis 
of the External oblique and the tendon 
of the Rectus abdominalis muscles. 
The deep fibres pass transversely 
across the symphysis, and are blended 
with the interpubic disk. 

The posterior pubic ligament consists 
of a few thin, scattered fibres which 
unite the two pubic bones posteriorly. 
The superior pubic ligament Qiga- 
mentum pubicum superhis) (Fig. 238) 
is a band of fibres which connects 
the two pubic bones superiorly. 

The inferior pubic or subpubic 
ligament Qigamentum arciiatit m pubis) 
(Fig. 238) is a thick, triangular arch 
of ligamentous fibres, connecting the 
two pubic bones below and forming the upper boundary of the pubic arch. 
Above, it is blended with the articular disk; laterally it is united with the descend- 
ing rami of the pubis. Its fibres are closely connected and have an arched 
direction. Its lower margin is separated from the triangular ligament of the 
perineum by a gap, through which runs the dorsal vein of the penis. 

The interpubic disk (lamina fibrocartilaginea interpubica) (Fig. 242) consists 
of a disk of fibrocartilage connecting the surfaces of the pubic bones in front. 
Each of the two surfaces is covered by a thin layer of hyaline cartilage whicli is 
firmly connected to the bone by a series of nipple-like processes which accurately 
fit within corresponding depressions on the osseous surfaces. These apposed 
cartilaginous surfaces are connected by an intermediate stratum of fibrous 
tissue and fibrocartilage which varies in thickness in different subjects. It 
often contains a cavity (cavwrn articulare) in its centre, probably formed by 
the softening and absorption of the fibrocartilage, since it rarely appears before 
the tenth year of life, and is not lined by synovial membrane. It is larger in the 
female than in the male. It is most frequently limited to the upper and back 




Fig. 242. — Vertical section of the symphysis pubi> 
Made near its posterior surface. 



STERNOCLAVICULAR ARTICULATION 



295 



part of the joint, but it occasionally reaches to the front, and may extend the 
entire length of the cartilage. This cavity may sometimes be demonstrated by 
making a vertical section of the symphysis pubis near its posterior surface 
(Fig. 242). 

The obturator ligament is more properly regarded as analogous to the mus- 
cular fasciae, with which it will be described. 



ARTICULATIONS OF THE UPPER EXTREMITY. 



The articulations of the upper extremity may be arranged in the following 
groups : 



I. Sternoclavicular Articulation. 
II. Acromioclavicular Articulation. 

III. Ligaments of the Scapula. 

IV. Shoulder-joint. 
V. Elbow-joint. 

VI. Radioulnar Articulations. 



VII. Wrist-joint. 

VIII. Articulations of the Carpal Bones. 
IX. Carpometacarpal Articulations. 
X. Metacarpophalangeal Articula- 
tions. 
XI. Articulations of the Phalanges. 



I. Sternoclavicular Articulation (Articulatio Stemoclavicularis) (Fig. 243). 

The sternoclavicular is an arthrodial joint. The parts entering into its forma- 
tion are the sternal end of the clavicle, the upper and lateral part of the first piece 
of the sternum, and the cartilage of the first rib. The articular surface of the 




Fig. 243. — Sternoclavicular articulation. Anterior 



sternum is covered with hyaline cartilage. The articular surface of the clavicle 
is much larger than that of the sternum, and invested with a layer of hyaline 
cartilage' which is considerably thicker than that on the latter bone. The liga- 
ments of this joint are the 



Capsular. 

Anterior Sternoclavicular. 

Posterior Sternoclavicular. 



Interclavicular. 
Costoclavicular. 
Articular Disk. 



1 According to Bruch, the sternal 
cartilaginous in structure. 



nd of the clavicle is covered by a tissue which is rather fibrous than 



296 THE ARTICULATIONS, OB JOINTS 

The capsular ligament {capsula articularis) completely surrounds the articula- 
tion, consisting of fibres of varying degrees of thickness and strength. Those 
in front and behind are of considerable thickness, and form the anterior and 
posterior sternoclavicular ligaments; but those above and below, especially in 
the latter situation, are thin and scanty. 

The anterior sternoclavicular ligament (Ikjamenium, sternodavicnlare) (Fig. 
243) is a part of the capsule. It is a broad band of fibres which covers the anterior 
surface of the articulation, being attached, above, to the upper and front part 
of the inner extremity of the clavicle, and, passing obliquely downward and 
inward, is attached, below, to the upper and front part of the first piece of the 
sternum. This ligament is covered, m front, by the sternal portion of the Sterno- 
mastoid and the integument; behind, it is in relation with the articular disk and 
the two synovial membranes. 

The posterior sternoclavicular ligament, also a part of the capsule, is a band 
of fibres which covers the posterior surface of the articulation, being attached, 
above, to the upper and back part of the inner extremity of the clavicle, and. 
passing obliquely downward and inward, is attached, below, to the upper and 
back part of the first piece of the sternum. It is in relation, in fro7it, with the 
articular disk and synovial membranes; behind, with the Sternohyoid and 
Sternothyroid muscles. 

The interclavicular ligament (ligamentum interdaviculare) (Fig. 243) is a flat- 
tened band which varies considerably in form and size in different individuals; 
it passes in a curved direction from the upper part of the inner extremity of one 
clavicle to the other, and is also attached to the upper margin of the sternum. 
It is in relation, in front, with the integument; behind, with the Sternothyroid 
muscles. 

The costoclavicular or rhomboid ligament Qicjamentum costoclavicidare) (Fig. 
243) is short, flat, and strong; it is of a rhomboid form, attached, belotv, to the 
upper and inner part of the cartilage of the first rib; it ascends obliquely back- 
ward and outward, and is attached, above, to the rhomboid depression on the 
under surface of the clavicle. It is in relation, in front, with the tendon of origin 
of the Subciavius; behind, with the subclavian vein. 

The articular disk (discus articularis) (Fig. 243) is a flat and nearly circular 
meniscus, interposed between the articulating surfaces of the sternum and clavicle. 
It is attached, above, to the upper and posterior border of the articular surface 
of the clavicle; beloiv, to the cartilage of the first rib, at its junction with the 
sternum; and by its circumference, to the anterior and posterior sternoclavicular 
and the interclavicular ligaments. It is thicker at the circumference, especially 
its upper and back part, than at its centre or below. It divides the joint into 
two cavities, each of which is furnished with a separate synovial membrane. 

Synovial Membrane. — Of the two synovial membranes found in this articulation, one is 
reflected from the sternal end of the clavicle over the adjacent surface of the articular disk and 
cartilage of the first rib; the other is placed between the articular surface of the sternum and 
adjacent surface of the articular disk; the latter is the larger of the tT\-o. 

Movements. — This articulation is the centre of the movements of the shoulder, and admits 
of a limited amount of motion in nearly every direction — upward, downward, backward, for- 
ward — as well as circumduction. When these movements take place in the joint, the clavicle 
in its motion carries the scapula with it, this bone gliding on the outer surface of the thorax. This 
joint therefore forms the centre from which all movements of the supporting arch of the shoulder 
originate, and is the only point of articulation of this part of the skeleton with the trunk. "The 
movements attendant on elevation and depression of the shoulder take place between the clavicle 
and the articular disk, the bone rotating upon the ligament on an axis drawn from before back- 
ward through its own articular facet. When the shoulder is moved forward and backward, the 
clavicle, with the articular disk, rolls to and fro on the articular surface of the sternum, revolving, 
■with a gliding movement, around an axis drawn nearly vertically through the sternum. In the 
circumduction of the shoulder, which is compounded of these two inovements, the clavicle revolves 



ACROMIOCLAVICULAR ARTICULATION 297 

upon the articular disk, and the latter, with the clavicle, rolls upon the sternum."' Elevation 
of the clavicle is principally limited by the costoclavicular ligament; depression by the inter- 
clavicular. The muscles which raise the clavicle, as in shrugging the shoulder, are the upper 
fibres of the Trapezius, the Levator anguli scapulae, the clavicular head of the Sternomastoid, 
assisted to a certain extent by the two Rhomboids, which pull the vertebral border of the scapula 
backward and upward, and so rai^c (he clavicle. The ilrjircssioii iif (lie chivicle is principally 
effected by gravity, assisted liy iln- SuUclavius, Pec'omlis niiimi-, ;iiiil Idwcr fibres of the Trape- 
zius. It is drawn backward \i\ the ifhomboids and the middle and luwcr liUrcs of the Trapezius; 
smA forward by theSerratus magnus and Pectoralis minor. 

Surface Form. — The position of the sternoclavicular joint may be easily ascertained by feeling 
the enlarged sternal end of the collar-bone just external to the long, cord-like, sternal origin 
of the Sternomastoid muscle. If this muscle is relaxed by bending the head forward, a depres- 
sion just internal to the end of the clavicle, and between it and the sternum, can be felt, indi- 
cating the exact position of the joint, which is subcutaneous. When the arm hangs by the side, 
the cavity of the joint is V-shaped. If the arm is raised, the bones become more closely approxi- 
mated, and the cavity becomes a mere slit. 

Applied Anatomy. — The strength of this joint mainly depends upon its ligaments, and it 
is because of the ligaments and because the force of a blow is generally transmitted along the 
long axis of the clavicle, that dislocation so rarely occurs, and that the bone is generally broken 
rather than displaced. When dislocation does occur, the course which the displaced bone takes 
depends more upon the direction in which the violence was applied than upon the anatomical 
construction of the joint; it may be either forward, backward, or upward. A complete upward 
dislocation is also inward. A complete forward or backward dislocation is also inward and 
downward. The chief point worthy of note, as regards the construction of the joint, in regard to 
dislocations, is the fact that, owing to the shape of the articular surfaces being so little adapted 
to each other, and that the strength of the joint mainly depends upon the ligaments, the dis- 
placement when reduced is very liable to recur, and hence it is extremely difficult to keep the 
end of the bone in its proper place, and it may be necessary to incise the soft parts and wire the 
bone in place. 



II. Acromioclavicular or Scapuloclavicular Articulation (Articulatio 
Acromioclavicularis) (Fig. 244). 

The acromioclavicular is an arthrodial joint formed between the outer ex- 
tremity of the clavicle and the inner margin of the acromion process of the scapula. 
The ligaments which surround the joint form a capsule. The ligaments of this 
articulation are the 

Superior Acromioclavicular. f Trapezoid 

Inferior Acromioclavicular. Coracoclavicular -! and 

Articular Disk. [ Conoid. 

Tlie superior acromioclavicular ligament (Ugamentum acromiodavindare) (Figs 
244 and 245) is a portion of the joint capsule. It is a quadrilateral band which 
covers the superior part of the articulation, extending between the upper part of 
the outer end of the clavicle and the adjoining part of the upper surface of the 
acromion. It is composed of parallel fibres which interlace with the aponeurosis 
of the Trapezius and Deltoid muscles; below, it is in contact with the articular 
disk (when it exists) and the synovial membranes. 

The inferior acromioclavicular ligament, somewhat thinner than the preceding, 
and, like it, a portion of the capsule, covers the under part of the articulation 
and is attached to the adjoining surfaces of the two bones. It is in relation, 
above, with the synovial membranes, and in rare cases with the articular disk; 
below, with the tendon of the Supraspinatus. These two ligaments are con- 
tinuous with each other in front and behind, and form a complete capsule around 
the joint. 

' Humphry, On the Human Skeleton, p. 402. 



298 THE ARTICULATIONS, OB JOINTS 

The articular disk {discus articularis) is frequently absent in this articulation. 
When the meniscus exists it is generally incomplete and only partially separates 
the articular surfaces, and occupies the upper part of the articulation. More 
jarely it completely separates the joint into two cavities. 

The Synovial Membrane. — There is usually only one synovial membrane in this articu- 
lation, but when a complete articular disk exists there are two synovial membranes. 

The coracoclavicular ligament (ligamentum coracoclaviculare) (Figs. 244 and 
245) serves to connect the clavicle with the coracoid process of the scapula. It 
does not properly belong to this articulation, but as it forms a most efficient means 
in retaining the clavicle in contact with the acromial process, it is usually described 
with it. It consists of two fasciculi, called the trapezoid and conoid ligaments. 




Fig. 244. — The left shoulder-joint, scapuloclavicular articulations, and proper ligaments of the scapula. 

The trapezoid ligament (ligamentum trapezoidcum), the anterior and external 
■fasciculus, is broad, thin, and quadrilateral; it is placed obliquely between the 
coracoid process and the clavicle. It is attached, below, to the upper surface 
of the coracoid process; above, to the oblique line on the under surface of the 
clavicle. Its anterior border is free; its posterior border is joined with the conoid 
ligament, the two forming by their junction a projecting angle. 

The conoid ligament (ligamentum conoideum), the posterior and internal fas- 
ciculus, is a dense band of fibres, conical in form, the base being directed upward, 
the summit downward. It is attached, below, by its apex to a rough impression at 
the base of the coracoid process, internal to the trapezoid ligament ; above, by its 
expanded base, to the conoid tubercle on the under surface of the clavicle, and 
■ to a line proceeding internally from it for half an inch. These ligaments are 



PBOPEB LIGAMENTS OF THE SCAPITLA 299 

in relation, in front, with the Subclavius and Deltoid; behind, with the Trapezius. 
They serve to limit rotation of the scapula, the trapezoid limiting rotation forward, 
and the conoid backward. 

Movements. — The movements of this articulation are of two kinds: (1 j A gliding motion of 
the articular end of the clavicle on the acromion. (2) Rotation of the scapula forward and back- 
ward upon the clavicle, the extent of this rotation being limited by the two portions of the coraco- 
■clavicular ligament. 

The acromioclavicular joint has important functions in the movements of the upper extremity. 
It has been well pointed out by Sir George Humphry that if there had been no joint between 
the clavicle and scapula the circular movement of the scapula on the ribs (as in throwing both 
shoulders backward or forward) would have been attended with a greater alteration in the 
direction of the shoulder than is consistent with the free use of the arm in such position, and 
it would have been impossible to give a blow straight forward with the full force of the arm ; that 
is tisay, with the combined force of the scapula, arm, and forearm. "This joint," as he happily 
says^'is so adjusted as to enable either bone to turn in a hinge-like manner upon a vertical 
Axis drawn through the other, and it permits the surfaces of the scapula, like the baskets in a 
roundabout swing, to look the same way in every position, or nearly so." Again, when the whole 
Arch formed by the clavicle and scapula rises and falls (in elevation or depression of the shoul- 
ders), the joint between these two bones enables the scapula still to maintain its lower part in 
■contact with the ribs. 

Surface Form. — The position of the acromioclavicular joint can generally be ascertained by 
the sli^tly enlarged extremity of the outer end of the clavicle, which causes it to project above 
the leva^f the acrDuiion process of the scapula. Sometimes this enlargement is so considerable 
as to form a mundcd eminence, which is easily to be felt. The joint lies in the plane of a vertical 
line passing u|) the middle of the front of the arm. 

Applied Anatomy. — Owing to the slanting shape of the articular surfaces of this joint, the 
■commonest didocation is the passing of the acromion process of the scapula under the outer 
end of the clavicle; but dislocations in the opposite direction have been described. The first 
form of dislocation is produced by violent force applied to the scapula so as to drive the shoulder 
forward. The displacement in acromioclavicular dislocation is often incomplete, on account 
of the strong coracoclavicular ligaments which remain untorn. The same difficulty exists, as in 
the sternoclavicular dislocation, in maintaining the ends of the bone in apposition after reduction, 
and it may become necessary to wire them in place after incision of the soft parts. 



III. Proper Ligaments of the Scapula (Figs. 244, 245). 

The proper ligaments of the scapula pass between portions of that bone, but 
are not parts of an articulation. They are the 

Coracoacromial. Superior Transverse. 

Inferior Transverse. 

The coracoacromial ligament (ligamentum coracoacromiale) is a strong triangular 
band, extending between the coracoid and acromial processes. It is attached, 
by its apex, to the summit of the acromion just in front of the articular surface 
for the clavicle, and by its broad base to the whole length of the outer border of 
the coracoid process. Its posterior fibres are directed inward, its anterior fibres 
forward and inward. This ligament completes the vault formed by the coracoid 
and acromion processes for the protection of the head of the humerus. It is in 
relation, above, with the clavicle and under surface of the Deltoid muscle; below, 
with the tendon of the Supraspinatus muscle, a bursa being interposed. Its 
■Older border is continuous with a dense lamina that passes beneath the Deltoid 
upon the tendons of the Supra- and Infraspinatus muscles. This ligament is 
sometimes described as consisting of two marginal bands and a thinner inter- 
vening portion, the two bands being attached, respectively, to the apex and base 
of the coracoid process, and joining together at their attachment into the acromion 
process, ^^^len the Pectoralis minor is inserted, as sometimes is the case, into 



300 



THE ARTICULATIONS, OR JOINTS 



the capsule of the shoulder-joint instead of into the coracoid process, it passes 
between these two bands, and the intervening portion is then deficient. 

The superior transverse or suprascapular ligament (lit/amentum transversum 
scapulae swperius) (Figs. 245 and 246) converts the suprascapular notch into a 




Fig, 245. — Right clavicle and scapula with ligament, from without and somewhat from in front. (Spalteholz.) 




ELTOID. SUPHASPINATUS. 



TERES MAJ 



TEBEs MAJOR. Circumflex vessels. 
Fig. 246. — Vertical sections through the shoulder-joint, the 




Circumflex vessels. 
being vertical and hor 



SCAPULARIS. 

ntal. (.\fter Henle.) 



foramen. It is a thin and flat fasciculus, narrower at the middle than at the 
extremities, attached by one end to the base of the coracoid process, and by the 
other to the inner extremity of the scapular notch. The suprascapular nerve 
passes through the foramen; the suprascapular vessels pass over the ligament. 



SHO ULDER-JOINT 30 1 

An additional ligament, the inferior transverse or spinoglenoid ligament (Ji(j(i- 
mentum traiisversum scapulae Inferius), is sometimes found on the scapula, 
stretching from the outer border of the spine to the margin of the glenoid cavity. 
When present, it forms an arch under which the suprascapular vessels and nerve 
pass as they enter the infraspinous fossa. 

Movements. — The scapula is capable of being moved upward and downward, forward and 
backward, or, by a combination of these movements, circumducted on the wall of the thorax. The 
muscles which raise the scapula are the upper fibres of the Trapezius, the Levator anguli scapulae, 
and the two Rhomboids; those which depress it are the lower fibres of the Trapezius, the Pec- 
toralis minor, and, through the clavicle, the Subclavius. The scapula is drawn hackicard by the 
Rhomboids and the middle and lower fibres of the Trapezius, and forward by the Serratus 
magnus and Pectoralis ininor, assisted, when the arm is fixed, by the Pectoralis major. The 
mobility of the scapula is very considerable, and greatly assists the movements of the arm at the 
shoulder-joint. Thus, in raising the arm from the side the Deltoid and Supraspinatus can only 
lift it to a right angle with the trunk, the further elevation of the limb being effected by the Trape- 
zius and Serratus magnus moving the scapula on the wall of the thorax. This mobility is of 
special importance in ankylosis of the shoulder-joint, the movement of this bone compensating 
ito a very great extent for the immobility of the joint. 



IV. Shoulder-Joint (Articulatio Humeri) (Figs. 245, 246). 

The shoulder-joint is an enarthrodial or ball-and-socket joint. The bones enter- 
ing into its formation are the large globular head of the humerus, which is received 
into the shallow glenoid cavity of the scapula — an arrangement which permits 
of very considerable movement, while the joint itself is protected against dis- 
placement by the tendons which surround it and by atmospheric pressure. The 
ligaments do not maintain the joint surfaces in apposition, because when they 
alone remain the humerus can be separated to a considerable extent from the 
glenoid cavity; their use, therefore, is to limit the amount of movement. Above, 
the joint is protected by an arched vault, formed by the under surfaces of the 
coracoid and acromion processes, and the coracoacromial ligament. The articular 
surfaces are covered by a layer of hyaline cartilage; that on the head of the humerus 
is thicker at the centre than at the circumference, the reverse being the case in 
the glenoid cavity. The ligaments of the shoulder are the 

Capsular. Transverse Humeral. 

Coracohumeral. Glenoid.' 

The capsular ligament (capsula articularis) (Figs. 245 and 247) completely 
encircles the articulation, being attached, above, to the circumference of the 
glenoid cavity beyond the glenoid ligament, below, to the anatomical neck of the 
humerus, approaching nearer to the articular cartilage above than- in the rest 
of its extent. It is thicker above and below than elsewhere, and is remarkably 
loose and lax, and much larger and longer than is necessary to keep the bones 
in contact, allowing them to be separated from each other more than an inch 
— an evident provision for that extreme freedom of movement which is peculiar 
to this articulation. Its superficial surface is strengthened, above, by the Supra- 
spinatus; below, by the long head of the Triceps; behind, by the tendons of the 
Infraspinatus and Teres minor; and in front, by the tendon of the Subscapularis. 
The capsular ligament usually presents three openings: One anteriorly, below 
the coracoid process, establishes a communication between the synovial mem- 
brane of the joint and a bursa beneath the tendon of the Subscapularis muscle. 

1 The long tendon of origin of the Biceps brachii muscle also acts as one of the ligaments of this joint. See the 
observations on p. 267 on the function of the muscles passing over more than one joint. 



302 



THE ARTICULATIONS, OB JOINTS 



The second, which is not constant, is at the posterior part, where a communica- 
tion sometimes exists between the joint and a bursal sac belonging to the Infra- 
spinatus muscle. The third is seen between the two tuberosities, for the passage 
of tlie long tendon of the Biceps brachii muscle. It transmits a sac-like prolonga- 
tion of the synovial membrane, which ends as a blind pouch opposite the surgicaL 
neck of the bone. 

The coracohumeral ligament (ligamentum coracohumerale) (Fig. 244) is a broad 
band which strengthens the upper part of the capsular ligament. It arises from 
the outer border of the coracoid process, and passes obliquely downward and 
outward to the front of the gi'eat tuberosity of the humerus, being blended with 
the tendon of the Supraspinatus muscle. This ligament is intimately united tO' 
the capsular ligament throughout the greater part of its extent. 



SUPERIOR 

TRANSVERSE 

LIGAMENT 




Fig. 247. — Right shoulder-joint, frontal section, from behind. (Spalteholz.) 



Supplemental Bands of the Capsular Ligament. — In addition to the coracohumeral 
ligament, the capsular ligament is strengthened by supplemental bands in the 
interior of the joint, and can be best studied by opening the capsule from behind 
and removing the head of the humerus. One of these bands (Flood's ligament) 
passes from the anterior edge of the glenoid cavity to the lower part of the lesser 
tuberosity of the humerus. It is supposed to correspond with the ligamentum 
teres of the hip-joint. A second of these bands (Schlemm's ligament), is situated 
at the lower part of the joint, and passes from the under edge of the glenoid cavity 
to the under part of the neck of the humerus. A third, called the glenohumera.l 
ligament, is situated at the upper part of the joint. It is attached, above, to the 
apex of the glenoid cavity, close to the root of the coracoid process, and, passing 
downward along the inner edge of the tendon of the Biceps brachii, is attached, 
below, above the lesser tuberosity of the humerus, where it forms the inner boundary 



SHOULDER-JOINT 303 

of the upper part of the bicipital groove. It is a thin, ribbon-like band, occasion- 
ally quite free from the capsule. 

The transverse humeral ligament is a prolongation of the capsular ligament. 
It is a broad hand of fibrous tissue passing from the lesser to the greater tuber- 
osity of the humerus, and always limited to that portion of the bone which lies 
above the epiphyseal line. It converts the bicipital groove into an osseoaponeu- 
rotic canal, and is the homologue of the strong process of bone which connects 
the summits of the two tuberosities in the musk o.x. 

The glenoid ligament {labrum glenoidale) (Figs. 245 and 247) is a fibrocartilagi- 
nous rim, attached around the margin of the glenoid cavity. It is triangular on 
section, the thickest portion being fixed to the circumference of the cavity, the 
free edge being thin and sharp. It is continuous above with the long tendon 
of the Biceps muscle, which bifurcates at the upper part of the cavity into two 
fasciculi, and becomes continuous with the fibrous tissue of the glenoid ligament. 
This ligament deepens the cavity for articulation, and protects the edges of the 
bone. 

Synovial Membrane (Fig. 247). — The synovial membrane is reflected from the margin of 
the glenoid cavity over the fibrocartilaginous rim surrounding it; it is then reflected over the 
internal surface of the capsular ligament, covers the lower part and sides of the anatomical neck 
of the humerus as far as the cartilage covering the head of the bone. The long tendon of the 
Biceps brachii, which passes through the capsular ligament, is enclosed in a tubular sheath of 
synovial membrane (vagina mucosa intertubercularis), which is reflected upon it at the point 
vvhere it perforates the capsule, and is continued around it as far as the level of the surgical 
neck of the humerus. The tendon of the Biceps is thus enabled to traverse the articulation, but 
it is not contained in the interior of the synovial cavity. 

Bursse. — A large bursa, the subscapular bursa, exists between the joint capsule and the ten- 
don of the Subscapularis muscle. I'liis sa<' communicates with the shoulder-joint by means 
of an opening at the inner side of the ciipsular ligament. Occasionally another and smaller bursa, 
the infraspinatus bursa, exists beneath the tendon of the Infraspinatus. It communicates with 
the shoukier-joint by means of an opening in the outer surface of the capsule. The subdeltoid 
or subacromial bursa is placed between the under surface of the Deltoid muscle and the outer 
surface of the capsule. It does not communicate with the joint. The subcutaneous acromial 
bursa is between the surface and the summit of the acromion process. There is a bursa beneath 
the Coracobrachialis muscle, one beneath the Teres major, and one beneath the tendinous 
portion of the Latissimus dorsi. There is also a bursa between the tendon of insertion of 
the Pectoralis major muscle and the long head of the Biceps. 

The muscles in relation with the joint are, above, theSupraspinatus; beloiv, the long head of 
the Triceps; mfronf, the Subscapularis; behind, the Infraspinatus and Teres minor; wiihiii, the 
long tendon of the Biceps. The Deltoid is placed most externally, and covers the articulation 
on its outer side, as well as in front and behind. 

The arteries supplying the joint are articular branches of the anterior and posterior circum- 
flex, and the suprascapular. 

The nerves are derived from the circumflex and suprascapular. 

Movements. — The shoulder-joint is capable of movement in every direction, forward, back- 
ward, abduction, adduction, circumduction, and rotation. The humerus is drawn fonvard by 
the Pectoralis major, anterior fibres of the Deltoid, Coracobrachialis, and by the Biceps when 
the forearm is flexed; backward, by the Latissimus dorsi. Teres major, posterior fibres of the Del- 
toid, and by the Triceps when the forearm is extended; it is abducted (elevated) by the Del- 
toid andSupraspinatus; it is adducted (depressed) by the Subscapularis, Pectoralis major, Latis- 
simus dorsi, and Teres major; it is rotated outward by the Infraspinatus and Teres minor; and 
it is rotated inward by the Subscapularis, Latissimus dorsi. Teres major, and Pectoralis major. 

The most striking peculiarities in this joint are: (1 ) The large size of the head of the humerus 
in comparison with the depth of the glenoid cavity, even when supplemented by the glenoid 
ligament. (2) The looseness of the capsule of the joint. (3) The intimate connection of the cap- 
sule with the muscles attached to the head of the humerus. (4) The peculiar relation of the 
Biceps tendon to the joint. 

It is in consequence of the relative size of the two articular surfaces that the joint enjoys such 
free movement in every possible direction. When these movements of the arm are arrested in 
the shoulder-joint by the contact of the bony surfaces and by the tension of the corresponding 
fibres of the capsule, together with that of the muscles acting as accessory ligaments, they can 
be carried considerably farther by the movements of the scapula, involving, of course, motion at 



304 THE ARTICULATIONS, OR JOINTS 

the acromio- and sternoclavicular joints. These joints are therefore to be regarded as accessory 
structures to the shoulder-joint.' The extent of these movements of the scapula is very con- 
siderable, especially in extreme elevation of the arm, which movement is best accomplished 
when the arm is thrown somewhat forward and outward, because the margin of the head of the 
humerus is by no means a true circle; its greatest diameter is from the bicipital groove downward, 
inward, and backward, and the greatest elevation of the arm can be obtained by rolling its 
articular surface in the direction of this measurement. The great width of the central portion 
of the humeral head also allows of very free horizontal movement when the arm is raised to a 
rifht ancle, in which movement the arch formed by the acromion, the coracoid process, and the 
coracoacromial ligament constitutes a sort of supplemental articular cavity for the head of the 
bone. 

The looseness of the capsule is so great that the arm will fall about an inch from the scapula 
when the muscles are dissected from the capsular ligament and an opening made in it to remove 
the atmospheric pressure. The movements of the joint, therefore, are. not regulated by the 
capsule so much as by the surrounding muscles and by the pressure of the atmosphere — an 
arrangement which "renders the movements of the joint much more easy than they would 
otherwise have been, and permits a swinging, pendulum-like vibration of the limb when the 
muscles are at rest" (Humphry). The fact, also, that in all ordinary positions of the joint the 
■capsule is not put on the stretch enables the arm to move freely in all directions. Extreme 
movements are checked by the tension of appropriate portions of the capsule, as well as by the 
interlocking of the bones. Thus it is said that "abduction is checked by the contact of the great 
tuberosity with the upper edge of the glenoid cavity, adduction by the tension of the coraco- 
humeral ligament" (Beaunis et Bouchard). Cleland^ maintains that the limitations of move- 
ment at the shoulder-joint are due to the structure of the joint itself, the glenoid ligament fitting, 
in different positions of the elevated arm, into the anatomical neck of the humerus. 

Cathcart^ has pointed out that in abducting the arm and raising it above the head, the scapula 
TOtates throughout the whole movement with the exception of a short space at the beginning and 
at the end; that the humerus moves on the scapula not only from the hanging to the horizontal 
position, but also in passing upward as it approaches the vertical above; that the clavicle moves 
not only during the second half of the movement but in the first as well, though to a less extent — 
i. p., the scapula and clavicle are concerned in the first stage as well as in the second; and that 
the humerus is partly involved in the second as well as chiefly in the first. 

The intimate union of the tendons of the four short muscles with the capsule converts these 
muscles into elastic and spontaneously acting ligaments of the joint, and it is regarded as being 
also intended to prevent the folds into which all portions of the capsule would alternately fall in 
the varying positions of the joint from being driven between the bones by the pressure of the 
atmosphere. 

The peculiar relations of the Biceps tendon to the shoulder-joint appear to subserve various 
purposes. In the first place, by its connection with both the shoulder and elbow the muscle 
harmonizes the action of the two joints, and acts as an elastic ligament in all positions, in the 
manner previously adverted to.* .\^ext, it strengthens the upper part of the articular cavity, and 
prevents the head of the humerus from being pressed up against the acromion process, when the 
Deltoid contracts, instead of forming the centre of motion in the glenoid cavity. By its passage 
.along the bicipital groove it assists in rendering the head of the humerus steady in the various 
movements of the arm. ^Vhen the arm is raised from the side it assists the Supra- and Infra- 
spinatus in rotating the head of the humerus in the glenoid cavity. It also holds the head of the 
bone firmly in contact with the glenoid cavity, and prevents its slipping over its lower edge, or 
lieincf displaced by the action of the Latissimus dorsi and Pectoralis major, as in climbing 
and many other movements. 

Surface Form. — The direction and position of the shoulder-joint may be indicated by a line 
•drawn from the middle of the coracoacromial ligament, in a curved direction, with its con- 
vexity inward, to the innermost part of that portion of the head of the humerus which can be 
-felt in the axilla when the arm is forcibly abducted from the side. When the arm hangs by the 
side, not more than one-third of the head of the bone is in contact with the glenoid cavity, and 
three-quarters of its circumference is in front of a vertical line drawn from the anterior border 
•of the acromion process. 

Applied Anatomy. — Owing to the construction of the shoulder-joint and the freedom of 
movement which it enjoys, as well as in consequence of its exposed situation, it is more fre- 
■quently dislocated than any other joint in the body. Dislocations of the shoulder contribute 
about forty per cent, of the cases in tables of dislocations. Dislocation occurs when the arm 
is thrown into extreme abduction, and when, therefore, the head of the humerus presses against 
ithe lower and front part of the capsule, which is the thinnest and least supported part of the liga- 

i See p. 299. ^ Journal of Anatomy and Physiology, 1884, vol. xviii. 

8Ibid.,voI. xviii. < See p. 267. 



SHOULDEE^ JOINT 305 

ment. The rent in the capsule ahnost invarialily takes jilace in this situation, between the 
tendon of the Subscapularis and the Triceps, and thn)ui:i;h it the head of the bone escapes, so 
that the dislocation in most instances is primarily subijlinoid. The head of the bone does not 
usually remain in this situation, but generally assumes some other position, which varies accord- 
ing to the direction and amount of force producing the dislocation and the relative strength of 
the muscles in front and behind the joint. In consequence of the muscles at the back being 
weaker than those in front, and especially on account of the long head of the Triceps preventing 
the bone passing backward, dislocation forward is much more common than backward. The 
most frequent position which the head of the humerus ultimately assumes is on the front of the 
neck of the scapula, beneath the coracoid process, and hence named subcoracoid dislocation. 
Occasionally, in consequence, probably, of a greater amount of force being brought to bear on 
the limb, the head is driven farther inward, and rests on the upper part of the front of the thorax, 
beneath the clavicle (subclamcular). If the head of the bone passes under the Subscapularis 
muscle and also under the Teres major or the lower border of the Pectoralis major, the arm 
remains abducted, or even with the elbow raised above the head (luxatio erecta). Sometimes 
the humerus remains in the position in which it was primarily displaced, resting on the axillary 
border of the scapula {subijlenoid), and rarely it passes backward and remains in the infra- 
spinous fossa beneath the spine (subspinous). If dislocation frequently recurs the condition may 
be amended in some cases by exposing the capsule and putting tucks in it by means of sutures. 

An old unreduced dislocation is sometimes treated by incising the soft parts and returning 
the head of the humerus into the glenoid cavity. In other cases the head of the humerus is 
excised. Dislocation oi the long tendon of the Biceps muscle from the bicipital groove is a rare 
accident. When it occurs the arm is rigid in abduction, but the head of the humerus is found 
to be in the glenoid cavity. It is reduced by flexion of the elbow and rotation of the arm. Rup- 
ture of the long tendon of the Biceps is more common than dislocation of the tendon. After this 
injury the belly of the muscle is relaxed and is nearer than normal to the elbow; flexion of 
the forearm is much weakened, and is weaker in supination than it is in pronation. The head 
of the humerus passes forward and inward, and the condition is often mistaken for dislocation 
of the bone. 

If we desire to aspirate the shoulder-joint, place the arm against the side, flex the forearm at 
a right angle to the arm, carry the forearm across the front of the thorax, and enter the trocar 
below the acromion (De Vos). 

The shoulder-joint is sometimes the seat of all those inflammatory affection,?, both acute and 
chronic, which attack joints, though perhaps it suffers less frequently than some other joints of 
equal size and importance. Acute synovitis may result from injury, rheumatism, or pyemia, or 
may follow secondarily on the so-called acute epiphysitis of infants. It is attended with effusion 
into the joint, and when this occurs the capsule is evenly distended and the contour of the joint 
rounded. Special projections may occur at the site of the openings in the capsular ligament. 
Thus, a swelling may appear just in front of the joint, internal to the lesser tuberosity, from 
effusion into the bursa beneath the Subscapularis muscle; or, again, a swelling which is some- 
times bilobed may be seen in the interval between the Deltoid and Pectoralis major muscles, 
from effusion into the diverticulum, which runs down the bicipital groove with the tendon of the 
Biceps. The effusion into the synovial membrane can be best ascertained by examination from 
the axilla, where a soft, elastic, fluctuating swelling can usually be felt. The bursa beneath the 
Deltoid is sometimes ruptured by violence, and sometimes inflames, suppurates, or becomes 
tuberculous. 

Tuberculous arthritis not infrequently attacks the shoulder-joint, and may lead to total 
destruction of the articulation, when ankylosis may result or long-protracted suppuration may 
necessitate excision. This joint is also one of those which is most liable to be the seat of osteo- 
arthritis, and may also be affected in gout and rheumatism; or in locomotor ataxia, when it 
occasionally becomes the seat of Charcot's disease. 

E.xdsion of the shoulder-joint may be required in cases of arthritis (especially the tubercu- 
lous form) which have gone on to destruction of the articulation; in compound di^locaticms and 
fractures, particularly those arising from gunshot injuries, in which there has been extensive 
injury to the head of the bone; in some cases of old unreduced dislocation, where there is much 
pain; and possibly in some few cases of growth connected with the upper end of the bone. The 
operation is best performed by making an incision from the middle of the coracoacromial liga- 
ment down the arm for about three inches; this will expose the- bicipital groove and the tendon 
of the Biceps, which may be either divided or hooked out of the way, according as to whether it 
is implicated in the disease or not. The capsule is then freely opened, and the muscles attached 
to the greater and lesser tuberosities of the humerus divided. The head of the bone can then 
be thrust out of the wound and sawed off, or divided with a narrow saw in situ and subsequently 
removed. The section should be made, if possible, just below the articular surface, so as to 
leave the bone as long as possible. The glenoid cavity must then be examined, and gouged 
if carious. 

20 



306 



THE ARTICULATIONS, OB JOINTS 



V. Elbow-joint (Articulatio Cubiti) (Figs. 248, 249). 

The elbow is a ginglymus or hinge-joint. The bones entering into its forma- 
tion are the trochlea of the humerus, which is received into the greater sigmoid 
cavity of the ulna, and admits of the movements peculiar to such a joint — viz., 
flexion and extension; while the capitellum or radial head of the humerus articu- 
lates with the cup-shaped depression on the head of the radius; the circum- 
ference of the head of the radius articulates with the lesser sigmoid cavity of 
the ulna, allowing of the movement of rotation of the radius on the ulna, the 
chief action of the superior radioulnar articulation. The articular surfaces 
are covered by a thin layer of hyaline cartilage, and connected by a capsular 





Fig. 248. — Left elbow-joint, showing anterior 
and internal ligaments. 



Fig. 249. — Left elbow-joint, showing posterior 
and external ligaments. 



ligament (capsula articulafis) (Fig. 250) of unequal thickness, being especially 
thickened on its two sides and, to a less extent, in front and behind. These 
thickened portions are usually described as distinct ligaments under the following 
names: 



Anterior. 
Posterior. 



Internal Lateral. 
External Lateral, 



ELBOW JOINT 



307 



The orbicular ligament of the upper radio-ulnar articulation must also be 
reckoned among the ligaments of the elbow (see p. 310). 

The anterior ligament (Fig. 248) is a broad and thin fibrous layer which covers 
the anterior surface of the joint. It is attached, above, to the front of the internal 
condyle and to the front of the humerus immediately above the coronoid and 
radial fossae; belotv, to the anterior surface of the coronoid process of the ulna 
and to the orbicular ligament, being continuous on each side with the lateral 
ligaments. Its superficial fibres pass obliquely from the inner condyle of the 
humerus outward to the orbicular ligament. The middle fibres, vertical in 
direction, pass from the upper part of the coronoid depression and become partly 
blended with the preceding, but are mainly inserted into the anterior surface of 
the coronoid process. The 
deep or transverse set inter- 
sects these at right angles. 
This ligament is in relation, 
in front, with the Brachialis 
anticus muscle, except at its 
outermost part. 

The posterior ligament 
(Fig. 249) is a thin and loose 
membranous fold, attached, 
above, to the lower end of 
the humerus, above and at 
the sides of the olecranon 
fossa; below, to the groove 
on the upper and outer sur- 
faces of the olecranon. The 
superficial or transverse fibres 
pass between the adjacent 
margins of the olecranon 
fossa. The deeper portion 
consists of vertical fibres, 
some of which, thin and 
weak, pass from the upper 
part of the olecranon fossa to 
the margin of the olecranon; 
others, thicker and stronger, 
pass from the back of the 
capltellum of the humerus to 
the posterior border of the 
lesser sigmoid cavity of the 
ulna. This ligament is in 
relation, behind, with the 
tendon of the Triceps muscle 
and the Anconeus muscle. 

The internal lateral ligament (ligamentum collaterale ulnare) (Fig. 248) is 
a thick triangular band consisting of two portions, an anterior and posterior, 
united by a thinner intermediate portion. The anterior portion, directed obliquely 
forward, is attached, above, by its apex, to the front part of the internal condyle 
of the humerus; and, below, by its broad base, to the inner margin of the coronoid 
process. The posterior portion, also of triangular form, is attached, above, by 
its apex, to the lower and back part of the internal condyle; below, to the inner 
margin of the olecranon. Between these two bands a few intermediate fibres 
descend from the internal condyle to blend with a transverse band of ligamentous 




50. — Right elbow-joint, cut tlirough at right angles to the 
of the trochlea humeri, from the ulnar side. (Spalteholz.) 



308 



THE ARTICULATIONS, OR JOINTS 



tissue which bridges across the notch between the olecranon and coronoid pro- 
cesses. This ligament is in relation, internally, with the Triceps and Flexor 
carpi ulnaris muscles and the ulnar nerve, and gives origin to part of the Flexor 
sublimis digitorum muscle. 

The external lateral ligament {ligamenhmi collatemle radiale) (Fig. 249) is a 
short and narrow fibrous band less distinct than the internal, attached, above, 
to a depression below the external condyle of the humerus; below, to the orbicular 
ligament, some of its most posterior fibres passing over that ligament, to be 
inserted into the outer margin of the ulna. This ligament is intimately blended 
with the tendon of origin of the Supinator [brevis] muscle. 



Synovial Membrane (Fig. 250). — The synovial itiembrane is very extensive. It covers the 
margin of the articular surface of the humerus, and lines the coronoid and olecranon fossae on 
that bone; from these points it is reflected over the anterior, posterior, and lateral ligaments, 

and forms a pouch (recessus sacciformis) between 
the lesser sigmoid cavity, the internal surface of 
the orbicular ligament, and the circumference of 
the head of the radius. Projecting into the cavity 
is a crescentic fold of synovial membrane, between 
the radius and ulna, suggesting the division of the 
joint into two — one the humeroradial, the other the 
humeroulnar. 

Between the capsular ligament and the synovial 
membrane are three masses of fat — one, the largest, 
above the olecranon fossa, which is pressed into 
the fossa by the Triceps during flexion; a second, 
over the coronoid fossa; and a third, over the 
radial fossa. The two last-named pads are pressed 
into their respective fossse during extension. 

The muscles (Fig. 251) in relation with the joint 
are, in front, the Brachialis anticus; behind, the 
Triceps and Anconeus; externally, the Supinator 
[brevis] and the common tendon of origin of the 
Extensor muscles; internally, the common tendon 
of origin of the Flexor muscles, and the Flexor 
carpi ulnaris, with the ulnar nerve. 

The arteries supplying the joint are derived 
from the anastomosis between the superior pro- 
funda, inferior profunda, and anastomotica magna, 
branches of the brachial, with the anterior, pos- 
terior, and interosseous recurrent branches of the 
ulnar and the recurrent branch of the radial. 
These vessels form a complete chain of anasto- 
moses around the joint. 

The nerves are derived from the ulnar as it 
passes between the internal condyle and the olec- 
ranon ; a filament from the musculocutaneous, and 
two filaments from the median. 
Bursse.^The olecranon hva&a, {bursa snbcnfanea olecrani) is placed between the olecranon 
process and the cutaneous surface. A bursa exists between the tendon of the Biceps brachii 
and the tubercle of the radius (bursa bicipitoradialis); another between the Triceps tendon and 
the olecranon process {bursa subtendinea olecrani) ; a third between the cutaneous surface and the 
external condyle {bursa subcuianea epicondyli humeri lateralis) ; a fourth between the cutaneous 
surface and the internt,! condyle {bursa subcutanea epicondyli humeri ?nedialis); and a fifth 
internal to the Triceps ttndon at its insertion on the olecranon {bursa intratendi?iea olecrani). 

Movements. — The elbow-joint comprises three different portions — viz., the joint between 
the ulna and humerus, that between the head of the radius and the humerus, and the superior 
radioulnar articulation, described below. All these articular surfaces are invested by a common 
synovial membrane, and the movements of the whole joint should be studied together. The com- 
bination of the movements of flexion and extension of the forearm with those of pronation and 
supination of the hand, which is insured by the two being performed at the same joint, is essential 
to the accuracy of the various minure movements of the hand. 

The portion of the joint between the ulna and humerus is a simple hinge-joint, and allows 




Fig 2d1 ^ It I ) , I 

joint taken somewhat obhquelj d 
the radial aspect (A.fter Braune ) 



ELBOW-JOINT 309 

of movements of flexion and extension only. Owing to the obliquity of the trochlear surface of 
the humerus, this movement does not take place in a straight line. When the forearm is extended 
and supinated the axis of the arm is not in the same line as the axis of the forearm, but the axis 
of the arm forms an angle with the axis of the forearm, and the hand, with the forearm, is 
directed outward. During flexion, on the other hand, the forearm and the hand tend to approach 
the middle line of the body, and thus enable the hand to be easily carried to the face. The shape 
of the articular surface of the humerus, with its prominences and depressions accurately adapted 
to the opposing surface of the olecranon, prevents any lateral movement. Flexion is produced 
by the action of the Biceps and Brachialis anticus, assisted by the muscles arising from the inter- 
nal condyle of the humerus and by the Brachioradialis; extension, by the Triceps and Anconeus, 
assisted by the Extensors of the wrist and by the Extensor communis digitorum and Extensor 
minimi digiti. 

The joint between the head of the radius and the capitellum or radial head of the humerus 
is an arthrodial joint. The bony surfaces would of themselves constitute an enarthrosis, and 
allow- of the movement in all directions were it not for the orbicular ligament by which the head 
of the radius is bound down firmly to the lesser sigmoid cavity of the ulna, an arrangement which 
prevents any lateral separation of the two bones. It is to the same ligament that the head of 
the radius owes its security from dislocation, which would otherwise constantly occur as a con- 
sequence of the shallowness of the cup-like surface on the head of the radius. In fact, but for 
this ligament the tendon of the Biceps would be liable to pull the head of the radius out of joint.' 
In complete extension the head of the radius glides so far back on the outer condyle that its 
edge is plainly felt at the back of the articulation. Flexion and extension of the elbow-joint are 
limited by the tension of the structures on the front and back of the joint, the limitation of flexion 
being also aided by the soft structures of the arm and forearm coming in contact. 

In combination with any position of flexion or extension the head of the radius can be rotated 
in the upper radioulnar joint, carrying the hand with it. The hand is directly articulated to the 
lower surface of the radius only, and the concave or sigmoid surface on the lower end of the 
radius travels around the lower end of the ulna. The latter bone is excluded from the wrist-joint 
(as will be seen in the sequel) by the articular disk. Thus, rotation of the head of the radius 
around an axis which passes through the centre of the radial head of the humerus imparts circular 
movement to the hand through a very considerable arc. 

Surface Form. — If the forearm be slightly flexed on the arm, a curved crease or fold with 
its convexity downward may be seen running across the front of the elbow, extending from one 
condyle to the other. The centre of this fold is some slight distance above the line of the joint. 
The position of the radiohumeral portion of the joint can be at once ascertained by feeling for a 
slight groove or depression between the head of the radius and the capitellum of the humerus at 
the back of the articulation. 

Applied Anatomy. — From the great breadth of the joint, and the manner in which the articular 
surfaces are interlocked, and also on account of the strong lateral ligaments and the support 
which the joint derives from the mass of muscles attached to each condyle of the humerus, 
lateral displacement of the bones is very uncommon, whereas antero-posterivr dislocation, on 
account of the shortness of the antero-posterior diameter, the weakness of the anterior and 
posterior ligaments, and the want of support of muscles, much more frequently takes place, 
dislocation backward taking place when the forearm is in a position of extension, and forward 
when in a position of flexion. For, in the former position, that of extension, the coronoid process 
is not interlocked into the coronoid fossa, and loses its grip to a certain extent, whereas the 
olecranon process is in the olecranon fossa, and entirely prevents displacement forward. On 
the other hand, during flexion, the coronoid process is in the coronoid fossa, and prevents dis- 
location backward, while the olecranon loses its grip and is not so efficient, as during extension, 
in preventing a forward displacement. When lateral dislocation does take place, it is generally 
incomplete. 

Dislocation of the elbow-joint is of common occurrence in children, far more common than 
dislocation of any other articulation. In lesions of this joint there is often very great difficultv in 
ascertaining the exact nature of the injury. Sprain of the elbow is a very common injury in child- 
hood. Injury to the radiohumeral joint is frequently ]>roduced by lifting a child by the hand, 
as in swinging it over a gutter. The Supinator [brevis], which under normal circumstances would 
retain the head of the radius against the capitellum of the humerus, is unable to do so, the radio- 
humeral articulation receives the force and the orbicular ligament undergoes upward displace- 
ment, is caught between the head of the radius and the capitellum, and jams the joint. This 
injury is often called subluxation of the head of the radius. 

The elbow-joint is occasionally the seat of acute synovitis. The synovial membrane then 
becomes distended with fluid, the bulging showing itself principally around the olecranon process; 
that is to say, on its inner and outer sides and above, in consequence of the laxness of the 

' Humphry, op. cit.. p. 419. 



310 THE ARTICULATIONS, OB JOINTS 

posterior ligament. Occasionally, a weE-marked, triangular projection may be seen on the outer 
side of the olecranon, from bulging of the synovial membrane beneath the Anconeus muscle. 
A^ain, there is often some swelling just above the head of the radius, in the line of the radio- 
humeral joint. There is generally not much swelling at the front of the joint, though sometime'^ 
deep-seated fulness beneath the Brachialis anticus may be noted. When suppuration occurs rlifj 
abscess usually points at one or other border of the Triceps muscle; occasionally the pus dis- 
charges itself in front, near the insertion of the Brachialis anticus muscle. Chronic synovitis, 
usually of tuberculous origin, is of common occurrence in the elbow-joint; under these circum- 
stance's the forearm tends to assume the position of semiflexion, which is that of greatest ease 
and relaxation of ligaments. It should be borne in mind that should ankylosis occur in this or 
the extended position, the limb will not be nearly so useful as if it becomes ankylosed in a position 
of rather less than a right angle. Loose cartilages- are sometimes met with in the elbow-joint, 
not so commonly, however, as in the knee; nor do they, as a rule, give rise to such urgent symp- 
toms. They rarely require operative interference. The elbow-joint is also sometimes affected 
with osteoarthritis, but this affection is less common in this articulation than in some other 
of the larger joints. Bursitis about the elbow, generally known as miners' elboiv, is not 
uncommon. 

Excision of the elbow is principally required for one of three conditions — viz., tuberculous 
arthritis, injury and its results, and ankylosis in a positior. which greatly impairs the useful- 
ness of the limb; but may be necessary for some other rarer conditions, such as disorganizing 
arthritis after pyemia, unreduced dislocation, and osteoarthritis. The results of the operation 
are, as a rule, more favorable than those of excision of any other joint, and it is one, therefore, 
that the surgeon should never hesitate to perform, especially in the first three of the conditions 
mentioned above. The operation is best performed by a single vertical incision down the back 
of the joint, a transverse incision, over the outer condyle, being added if the parts are much 
thickened and fixed. A straight incision is made about four inches long, the mid-point of which 
is on a level with and a little to the inner side of the tip of the olecranon. This incision is made 
down to the bone, through the substance of the Triceps muscle. The operator with the point 
of his knife, and guarding the soft parts with his thumb-nail, separates them from the bone. 
In doing this there are two structures which he should carefully avoid — the ulnar nerve, which 
lies parallel to his incision, but a little internal, as it courses down between the internal condyle 
and the olecranon process, and the prolongation of the Triceps into the deep fascia of the fore- 
arm over the Anconeus muscle. Having cleared the bones and divided the lateral and posterior 
lio-aments, the forearm is strongly flexed and the ends of the bone turned out and sawed off. The 
section of the humerus should be through the base of the condyles, that of the ulna and radius 
should be just below the level of the lesser sigmoid cavity of the ulna and the neck of the radius. 
In this operation the object is to obtain such fibrous union as shall allow free motion of the 
bones of the forearm: and, therefore, passive motion must be commenced early, that is to say, 
about the tenth day. 

VT. Radioulnar Articulation (Articulatio Radioulnaris) . 

The articulation of the radius with the ulna is effected by ligaments which 
connect both extremities as well as the shafts of these bones. It may, conse- 
quently, be subdivided into three articulations: (1) The superior radioulnar, 
which is a portion of tlie elbow-joint; (2) the middle radioulnar; and (3) the 
inferior radioulnar articulations. 



1. Superior Articulation (Articulatio Radioulnaris Proximalis). 

This articulation is a trochoid or pivot-joint. The bones entering into its forma- 
tion are the inner side of the circumference of the head of the radius rotating 
within tlie lesser sigmoid cavity of the ulna. Its only ligament is the annular 
or orbicular. 

The orbicular or annular ligament (Jigamenium annulare radii) (Figs. 248, 249, 
and 2.52) is a strong, flat band of ligamentous fibres which surrounds the head of 
the radius and retains it in firm connection with tire lesser sigmoid cavity of the 
ulna. It fonns about four-fifths of an osseofibrous ring, attached by each end to 
tlie extremities of the lesser sigmoid cavity, and is smaller at the lower part of its 



BA DIO ULNAR A R TICULA TION 



311 



ORBICULAR 



circumference than above, by which means the head of the radius is more securely 
held in its position. Its outer surface is strengthened by the external lateral 
ligament of the elbow, and affords 
origin to part of the Supinator [brevis] 
muscle. Its inner surface is smooth, 
and lined with synovial membrane. 
The synovial mem brane is continuous 
with that which lines the elbow-joint. 

Movements. — The movement which takes 
place in this articulation is limited to rotation 
of the head of the radius within the orbicular 
ligament, and upon the lesser sigmoid cavity 
of the ulna; the axis of rotation passes through 
the centre of the capitellum of the humerus. 
Rotation forward is called pronation; rota- 
tion backward, supinaiion. Supination is 
performed by the Biceps and Supinator 
[brevis], assisted to a slight extent by the Ex- 
tensor muscles of the thumb and, in certain 
positions, by the Brachioradialis. Pronation 
is effected by the Pronator teres and Pronator 
quadratus, assisted, in some positions, by the 
BrJichioradialis. 

Surface Form. — The position of the su- 
perior radioulnar joint is marked on the 
surface of the body by the little dimple on 
the back of the elbow, which indicates the 
position of the head of the radius. 

Applied Anatomy.— D;.?/oca(?o». of the 
head of the radius alone is not an uncommon 
accident, and occurs most frequently in young 
persons from falls on the hand when the fore- 
arm is extended and supinated, the head of 
the bone being displaced forward. It is at- 
tended by rupture of the orbicular ligament. 
Occasionally a peculiar injury, which is sup- 
posed to be a subluxation, occurs in young 
children in lifting them from the ground by 
the hand or forearm. It is believed that the 
head of the radius is displaced downward or 
the orbicular ligament upward, and the upper 
border of the ligament becomes folded over 
the head of the radius, between it and the 
capitellum of the humerus. 



2. Middle R.\dioulnar Lig.\ments. ' 

The interval between the shafts of 
the radius and ulna is occupied by two 

ligaments. 



Oblique. 
Interosseous. 

The oblique ligament (chorda ohli- ^'°- '""-^^eX ^4lt\■s1LV'°Ts^™teh;lz^ *'"' "'"" 
qua) (Figs. 248 and 252) is a small, flat- 
tened fibrous band which extends obliquely downward and outward from the 
tubercle of the ulna at the base of the coronoid process to the radius a little below 
the bicipital tuberosity. Its fibres run in the opposite direction to those of the 




312 



THE ARTICULATIONS, OB JOINTS 



interosseous ligament, and it appears to be placed as a substitute for it in the 
upper part of the interosseous interval. This ligament is sometimes wanting. 
The interosseous membrane (membrana interossea antehrachii) (Fig. 252) is a 
broad and thin plane of fibrous tissue descending obliquely downward and inward, 
from the interosseous ridge on the radius to that on the ulna. It is deficient 
above, commencing about an inch beneath the tubercle of the radius; is broader 
in the middle than at either extremity; and presents an oval aperture just above 
its lower margin for the passage of the anterior interosseous vessels to the back of 
the forearm. This ligament serves to connect the bones and to increase the extent 
of surface for the attachment of the deep muscles. Between its upper border 
and the oblique ligament an interval exists through which the posterior inter- 
osseous vessels pass to the dorsum of the forearm. Two or three fibrous bands 
are occasionally found on the dorsal surface of this membrane which descend 
obliquely from the ulna toward the radius, and which have consequently a direc- 
tion contrary to that of the other fibres. It is in relation, in front, by its upper 
three-fourths with the Flexor longus pollicis on the outer side, and with the 
Flexor profundus digitorum on the inner, lying upon the interval between which 
are the anterior interosseous vessels and nerve; by its lower fourth, with the Pro- 
nator quadratus; behind, with the Supinator [brevis]. Extensor ossis metacarpi 
pollicis, Extensor brevis pollicis. Extensor longus pollicis. Extensor indicis; and, 
near the wrist, with the anterior interosseous artery and posterior interosseous 



3. Inferior Articulation (Articulatio Radioulnaris Distalis). 

This is a pivot-joint, formed by the sigmoid cavity at the inner side of the lower 
end of the radius receiving the head of the ulna. The articular surfaces are 
covered by a thin layer of hyaline cartilage, and connected by a capsule, portions 
of which are usually described as distinct ligaments. The ligaments of the 
articulation are: 

Anterior Radioulnar. Posterior Radioulnar. 

Triangular Articular Disk. 

The anterior radioulnar ligament (Fig. 253) is a narrow band of fibres 
extending from the anterior margin of the sigmoid cavity of the radius to the 
anterior surface of the head of the ulna. 

The posterior radioulnar ligament (Fig. 254) extends between similar points 
on the posterior surface of the articulation. 

The triangular articular disk (discus articularis) (Figs. 252 and 256) is triangular 
in shape, and is placed transversely beneath the head of the ulna, binding the lower 
end of this bone and the radius firmly together. Its periphery is thicker than its 
centre, which is thin and occasionally perforated. It is attached by its apex 
to a depression which separates the styloid process of the ulna from the head of 
that bone; and by its base, which is thin, to the prominent edge of the radius, 
which separates the sigmoid cavity from the carpal articulating surface. Its 
margins are united to the ligaments of the wrist-joint. Its upper surface, smooth 
and concave, articulates with the head of the ulna, forming an arthrodial joint; 
its under surface, also concave and smooth, forms part of the wrist-joint and articu- 
lates with the cuneiform and inner part of the semilunar bone. Both surfaces 
are covered by a synovial membrane — the upper surface by one peculiar to the 
radioulnar articulation; the under surface, by the synovial membrane of the 
wrist. 



RADIOULNAR ARTICULATION 



3l3 



Synovial Membrane. — The synovial membrane (Fig. 256) of this articulation has been called, 
from its extreme looseness, the membrana sacciformis. It projects horizontally inward between 
the head of the ulna and the articular disk, and upward' between the radius and the ulna, forming 
a very loose cul-de-sac {reccssus sacciformis). The quantity of synovia which it contains is usually 
considerable. The inferior radioulnar joint does not communicate with the wrist-joint. 




radioulnar 
articulation. 



Carpometacarpal 
iculatimis. 



Fig. 253, — Ligaments of wrist and hand. Anterior viewv 



Inferior radioulnar 

articulation 

Wrist-joint 



Carpal articulations 



Carpometacarpal 

articulation 




Fig. 254. — Ligaments of wrist and hand. Posterior i 

Movements.— These consist of a movement of rotation through about 1 60 degrees of the lower 
end of the radius around an axis which corresponds to the centre of the head of the ulna. When 
the radius rotates forward, pronation of the forearm and hand is the result; and when backwaid, 
snpinaiion. It will thus be seen that in pronation and supination of the forearm and hand 
the radius describes a segment of a cone, the axis of which extends from the centre of the head 



314 THE ARTICULATIONS, OR JOINTS 

of the radius to the middle of the head of the ulna. In this movement, however, the ulna is 
not quite stationary, but rotates a little in the opposite direction. So that it also describes the 
segment of a cone, though of smaller size than that described by the radius. The movement 
■n-hich causes this alteration in the position of the head of the ulna takes place principally at the 
shoulder-joint by the rotation of the humerus, but possibly also to a slight extent at the elbow- 
joint.' 

Surface Form. — The position of the inferior radio-ulnar joint may be ascertained by feeling 
for a slight groove at the back of the ^\Tist, between the prominent head of the ulna and the 
lower end of the radius, when the forearm is in a state of almost complete pronation. 

VII. Radiocarpal or Wrist-joint (Articulatio Radiocarpea) (Figs. 253, 254). 

The wrist is a condyloid articulation. The parts entering into its formation 
are the lower end of the radius and under surface of the articular disk, which 
form together the receiving cavity, and the scaphoid, semilunar, and the cunei- 
form bones, which form the condyle. The articular surface of the radius and the 
under surface of the articular disk are the receiving cavity, forming together a 
transversely elliptical concave surface. The articular surfaces of the scaphoid, 
semilunar, and cuneiform bones form together a smooth, convex surface, the con- 
dyle, which is received into the concavity above mentioned. All the bony surfaces 
of the articulation are co\'ered by hyaline cartilage, and are connected by a capsule, 
which is divided into the following ligaments: 

External Lateral. Anterior. 

Internal Lateral. Posterior. 

The external lateral ligament Qigamentum collaterale carpi radiale) (Fig. 253) 
extends from the summit of the styloid process of the radius to the outer side of 
the scaphoid, some of its fibres being prolonged to the trapezium and annular 
ligament. 

The internal lateral ligament (llgamenttim collaterale carpi ulnars) (Fig. 253) 
is a rounded cord, attached, above, to the extremity of the styloid process of the 
ulna, and dividing, below, into two fasciculi, which are attached, one to the inner 
side of the cuneiform bone, the other to the pisiform bone and annular ligament. 

The anterior or volar ligament (ligamentum, radiocarpeum volare) (Fig. 253) 
is a broad, membranous band, attached, above, to the anterior margin of the 
lower end of the radius, to its styloid process, and to the ulna; its fibres pass down- 
ward and inward to be inserted into the palmar surface of the scaphoid, semilunar, 
and cuneiform bones. Some of the fibres are' continued to the os magnum. In 
addition to this broad membrane there is a distinct rounded fasciculus, superficial 
to the rest, which passes from the base of the styloid process of the ulna to the semi- 
lunar and cuneiform bones. This ligament is perforated by numerous apertures 
for the passage of vessels, and is in relation, in front, with the tendons of the 
Flexor profundus digitorum and of the Flexor longus pollicis. 

The posterior or dorsal ligament {ligamentum radiocarpeum dorsale) (Fig. 254), 
thinner and weaker than the anterior, is attached, above, to the posterior border 
of the lower end of the radius ; its fibres pass obliquely downward and inward, to 
be attached to the dorsal surface of the scaphoid, semilunar, and cuneiform bones, 
and are continuous with those of the dorsal carpal ligaments. This ligament 
is in relation, behind, with the Extensor tendons of the fingers. 

Synovial Membrane.— The synovial membrane (Fig. 255) lines the inner surface of the 
ligaments above described, extending from the lower end of the radius and articular disk above 

' See Hultkrantz, Das Ellenbogen Gelenk und seine Mechanik, Jena, 1S97. 



ARTICULATIOJ^ti OF THE CARPUS 315 

to the articular surfaces of the carpal bones below. It is loose and lax, and presents numerous 
fdlils, cs])ccia]ly behind. 

The arteries supplying the joint are the anterior and posterior carpal branches of the radial 
and ulnar, the anterior and posterior interosseous, and some ascending branches from the deep 
palmar arch. 

The nerves are derived from the ulnar and posterior interosseous. 

Movements. — The movements permitted in this joint are volar flexion, dorsi-flexion, 
abduction, addudion, and circumduction. Its actions will be further studied with those of the 
carpus, with which they are combined. 

Surface Form. — The line of the radiocarpal joint is on a level with the apex of the styloid 
process of the ulna. 

Applied Anatomy. — The wrist-joint is rarely dislocated, its strength depending mainly upon 
the numerous strong tendons which surround the articulation. Its security is further pro- 
vided for by the number of small bones of which the carpus is made up, and which are united 
by very strong ligaments. The slight movement which takes place between the several bones 
serves to break the jars that result from falls or blows on the hand. Dislocation backward, 
which is the more common dislocation, simulates to a considerable extent CoUes' fracture of the 
radius, and is apt to be mistaken for it. The diagnosis can be easily made out by observing 
the relative position of the styloid processes of the radius and ulna. In the natural condition 
the styloid process of the radius is on a lower level — i. e., nearer the ground — when the arm hangs 
by the side, than that of the ulna, and the same would be the case in dislocation. In Colles' 
fracture, on the other hand, the styloid process of the radius is on the same or even a higher 
level than that of the ulna. 

The wrist-joint is occasionally the seat of acute synovitis, the result of traumatism or con- 
sequent upon rheumatic or pyemic conditions. When the synovial sac is distended with fluid, 
the swelling is greatest on the dorsal aspect of the wrist, and shows a general fulness, with some 
bulging between the tendons. The inflammation is prone to extend to the intercarpal joints and 
to attack also the sheaths of the tendons in the neighborhood. Chronic inflammation of the wrist 
is generally tuberculous, and often leads to similar disease in the synovial sheaths of adjacent 
tendons and of the intercarpal joints. The disease, therefore, when progressive, frequently 
leads to necrosis of the carpal bones, and the result is often unsatisfactory. 



VIII. Articulations of the Carpus (Articulatio Intercarpea) (Figs. 253, 254). 

These articulations may be subdivided into three sets: 

1. The Articulations of the First Row of Carpal Bones. 

2. The Articulations of the Second Row of Carpal Bones. 

3. The Articulations of the Two Rows with each other. 



1. Articulations of the First Row of Carpal Bones 

These are arthrodial joints. The ligaments connecting the scaphoid, semi- 
lunar, and cuneiform hones are: 

Dorsal. Palmar. 

Two Interosseous. 

The dorsal ligaments (llgameida intercarpea dorsalia) are placed transversely 
behind the bones of the first row; they connect the scaphoid and semilunar and 
the semihuiar and cimeiform. 

The palmar or volar ligaments (Ugamenta intercarpea volaria) connect the 
scaphoid and semilunar and the semilunar and cuneiform bones; they are weaker 
than the dorsal, and placed very deeply below the anterior ligament of the wrist. 

The interosseous ligaments (ligamenta intercarpea interossea^ (Fig. 255) are tvi'o 
narrow bundles of fibrous tissue connecting the semilunar bone on one side with 
the scaphoid, and on the other with the cuneiform. They are on a level with 
the superior surfaces of these bones, and close the upper part of the spaces 



316 THE ARTICULATIONS, OB JOINTS 

between them. Their upper surfaces are smooth, and form with the bones the 
convex articular surfaces of the wrist-joint. 

The hgaments connecting the pisiform bone are: 

Capsular. Two Palmar Ligaments. 

The capsular ligament is a thin membrane which connects the pisiform bone 
to the cuneiform. It is lined by a separate synovial membrane. 

The two palmar ligaments are two strong fibrous bands which connect the 
pisiform to the unciform {ligamentum pisohamatum) , and to the base of the fifth 
metacarpal bone {ligainentum pisometacarpeum). 



2. Articulations of the Second Row of Carpal Bones. 

These are also arthrodial joints. The articular surfaces are covered with 
hyaline cartilage, and connected by the following ligaments: 

Dorsal. Palmar. 

Three Interosseous. 

The dorsal ligaments {ligamenta iniercarpea dorsalia) extend transversely from 
one bone to another on the dorsal surface, connecting the trapezium with the trape- 
zoid, the trapezoid with the os magnum, and the os magnum with the unciform. 

The palmar ligaments (^ligamenta iniercarpea volaria) have a similar arrange- 
ment on the palmar surface. 

The three interosseous ligaments (ligamenta intercarpea inierossea) (Fig. 255),. 
much thicker than those of the first row, are placed one between the os magnum 
and the unciform, a second between the os magnum and the trapezoid, and a 
third between the trapezium and trapezoid. The first of these is much the 
strongest, and the third is sometimes wanting. 



3. Articulations of the Two Rows of Carpal Bones with Each Other 
(Figs. 253, 254). 

The joint between the scaphoid, semilunar, and cuneiform, and the second 
row of the carpus, or the midcarpal joint, is made up of three distinct portions; 
in the centre the head of the os magnum and the superior surface of the unciform 
articulate with the deep, cup-shaped cavity formed by the scaphoid and semilunar 
bones, and constitute a sort of ball-and-socket joint. On the outer side the trape- 
zium and trapezoid articulate with the scaphoid, and on the inner side the unci- 
form articulates with the cuneiform, forming gliding joints. 

Sometimes a small ligament joins the navicular to the neck of the os magnum 
and is representative of the os centrale (p. 206) (Sutton). 

The ligaments are: 

Anterior. External Lateral. 

Posterior. Internal Lateral. 

The anterior or palmar ligaments (ligamenta intercarpea volaria) consist of 
short fibres, which pass, for the most part, from the palmar surface of the bones 
of the first row to the front of the os magnum. 



CARPOMETACARPAL ARTICULATIONS 317 

The posterior or dorsal ligaments (ligmnenta intercarpea dorsalis) consist of 
short, irregular bundles of fibres passing between the bones of the first and second 
row on the dorsal surface of the carpus. 

The lateral ligaments are very short; they are placed, one on the radial, the 
other on the ulnar side of the carpus; the former, the stronger and more distinct, 
■connecting the scaphoid and trapezium, the latter the cuneiform and unciform; 
they are continuous with the lateral ligaments of the wrist-joint. In addition to 
these ligaments, a slender interosseous band sometimes connects the os magnum 
and the scaphoid. 

Synovial Membrane (Fig. 255). — The synovial membrane of the carpus is very extensive; 
it passes from under the surface of the scaphoid, semilunar, and cuneiform bones to the upper 
sm-face of the bones of the second row, sending upward two prolongations — between the scaphoid 
and semilunar and the semilunar and cuneiform; sending downward three prolongations between 
the four bones of the second row, which are further continued onward into the carpometacarpal 
joints of the four inner metacarpal bones, and also for a short distance between the metacarpal 
bones. There is a separate synovial membrane between the pisiform and the cuneiform bones. 

Movements. — The articulation of the hand and wrist, considered as a whole, is divided into 
three parts: (1) The radius and the articular disk, (2) the meniscus,'^ formed by the scaphoid, 
semilunar, and cuneiform, the pisiform bone having no essential part in the movements of the 
hand; (.3) the hand proper, the metacarpal bones with the four carpal bones on which they are 
svipported — viz., the trapezium, trapezoid, os magnum, and unciform. These three elements 
form two joints: (1) The superior, wrist-joint proper, between the meniscus and bones of the 
forearm; (2) the inferior, transverse or midcarpal joint, between the hand and nHiiiscus. 

1. The articulation between the forearm and carpus is a true condyloid articulation, and 
therefore all movements but rotation are permitted. Flexion and extension are the most exten- 
sive, and of these a greater amount of extension than flexion is permitted on account of the 
articulating surfaces extending farther on the dorsal than on the palmar aspect of the carpal 
bones. In this movement the carpal bones rotate on a transverse axis drawn between the tips 
of the styloid processes of the radius and ulna. A certain amount of adduction (or ulnar flexion) 
and abduction (or radial flexion) is also permitted. Of these movements, the former is consider- 
ably greater in extent than the latter. In these movements the carpus revolves upon an antero- 
posterior axis drawn through the centre of the wrist. Finally, circumduction is permitted by 
the consecutive movements of adduction, extension, abduction, and flexion, with intermediate 
movements between them. There is no rotation, but this is provided for by the supination and 
pronation of the radius on the ulna. The movement of volar flexion is performed by the 
Flexor carpi radialis, the Flexor carpi ulnaris, and by the Palmaris longus; dorsi-flexion, by 
the Extensor carpi radialis longior et brevior and the Extensor carpi ulnaris; adduction (ulnar 
flexion), by the Flexor carpi ulnaris and the Extensor carpi ulnaris; and abduction (radial 
flexion), by the Extensors of the thumb and the Extensores carpi radialis longior et brevior 
and the Flexor carpi radialis. 

2. The chief movements permitted in the transverse or midcarpal joint are flexion, extension, 
and a slight amount of rotation. In flexion, and extension, which are the movements most freely 
enjoyed, the trapezium and trapezoid on the radial side and the unciform on the ulnar side 
glide forward and backward on the scaphoid and cuneiform respectively, while the head of the 
OS magnum and the superior surface of the unciform rotate in the cup-shaped cavity of the 
scaphoid and semilunar. Flexion at this joint is of greater range than extension. A very trifling 
amount of rotation is also permitted, the head of the os magnum rotating around a vertical axis 
drawn through its own centre, while at the same time a slight gliding movement takes place in 
the lateral portions of the joint. 

IX. Carpometacarpal Articulations (Articulationes Carpometacarpeae) (Fig. 254). 

1. Articulation of the Metacarpal Bone of the Thumb with the 
Trapezium (Articulatio Carpometacarpea Pollicis). 

This is a joint of reciprocal reception, and enjoys great freedom of movement, 
on account of the configuration of its articular surfaces, which are saddle-shaped, 

' Called meniscus because the bones composing it serve the essential purposes of an articular disk. 



318 THE ARTICULA TIONS, OR JOINTS 

so that, on section, each bone appears to be received into a cavity in the other, 
according to the direction in which they are cut. The joint is surrounded by a 
capsular ligament. 

The capsular ligament is thick and fibrous, but loose, and passes from the cir- 
cumference of the upper extremity of the metacarpal bones to the rough edge 
bounding the articular surface of the trapezium; it is thickest externally and behind, 
and lined with a separate synovial membrane. 

Movements. — In the articulation of the metacarpal bone of the thumb with the trapezium, 
the movements permitted are flexion, extension, adduction, abduction, and circumduction. When 
the joint is flexed the metacarpal bone is brought in front of the palm and the thumb is gradu- 
ally turned to the fingers. It is by this peculiar moveaent that the tip of the thumb is opposed 
to the other digits; for by slightly flexing the fiiif^ers the palmar surface oi the thumb can be 
brought in contact with their palmar surfaces. 



2. Articulations of the Metacarpal Bones of the Four Inner Fingers 
WITH THE Carpus (Articulationes Carpometacarpeae). 

The joints formed between the carpus and four inner metacarpal bones are 
arthrodial joints. The ligaments are: 

Dorsal. Palmar. 

Interosseous. 

The dorsal ligaments (Jigamenta carpometacarpea dorsalis), the strongest and 
most distinct, connect the carpal and metacarpal bones on their dorsal surface. 
The second metacarpal bone receives two fasciculi — one from the trapezium, 
the other from the trapezoid; the third metacarpal receives two — one from the 
trapezoid and one from the os magnum; the fourth, two — one from the os magnum 
and one from the unciform; the fifth receives a single fasciculus from the unciform 
bone, which is continuous with a similar ligament on the palmar surface, thus 
forming an incomplete capsule. 

The palmar ligaments (Ugamenta carpometacarpea volaria) have a somewhat 
similar arrangement on the palmar surface, with the exception of the third meta- 
carpal, which has three ligaments — an external one from the trapezium, situated 
above the sheath of the tendon of the Flexor carpi radialis; a middle one, from 
the OS magnum; and an internal one, from the unciform. 

The interosseous ligaments consist of short, thick fibres, which are limited to 
one part of the carpometacarpal articulation; they connect the contiguous inferior 
angles of the os magnum and unciform with the adjacent surfaces of the third 
and fourth metacarpal bones. 

Synovial Membrane. — The synovial membrane is a continuation of that between the two 
rows of carpal bones. Occasionally, the articulation of the unciform with the fourth and fifth 
metacarpal bones has a separate synovial membrane. 

The synovial membranes of the wrist and carpus (Fig. 255) are thus seen to be five in number. 
The first, the membrana saccifonnis of the inferior radioulnar articulation, passes from the 
lower end of the ulna to the sigmoid cavity of the radius, and lines the upper surface of the 
articular disk. The second passes from the lower end of the radius and articular disk above 
to the bones of the first row below. The third, the most extensive, passes between the contig- 
uous margins of the two rows of carpal bones — between the bones of the second row to the 
carpal extremities of the four inner metacarpal bones. The. fourth passes from the margin of 
the trapezium to the metacarpal bone of the thumb. The fifth passes between the adjacent 
margins of the cuneiform and pisiform bones. 



\ 



CA RPOMETA CA RPA L AR TICULA T10N8 



31& 



Movements. — The movement permitted in the carpometacarpal articulations of the four 
inner fingers is limited to a slight gliding of the articular surfaces upon each other, the extent 
of which varies in the different joints. Thus, the articulation of the metacarpal bone of the 
little finger is most movable, then that of the ring linger. The metacarpal bones of the index 
and middle fingers are almost immovable. 



MEMBRANA SACCI- 

FORMIS OF INFERIOR 

RADIO-ULNAR 

ARTICULATION 



TRIANGULAR 

ARTICULAR DISK 

STYLOID PROCESS 

OF ULNA 




ARTICULATION OF 
TRAPEZIUM AND 
METACARPAL BONE 
OF THUMB 



METACARPAL BONES 

Fig. 255.— Joints of the right hand, from the back of the hand. (Spalteholz.) 



3. Articulations of the Metacarpal Bones with Each Other (Articu- 
LATioNES Intermetacarpeae (Figs. 254, 255). 



The carpal extremities of the four inner metacarpal bones articulate with one 
another at each side by small surfaces covered with cartilages, and connected 
by dorsal, palmar, and interosseous ligaments. 

The dorsal ligaments {ligamenta hasium oss. metacarp. dorsalia) and palmar 
ligaments (liejamenta hasium oss. vietacarp. volaria) pass transversely from one 
bone to another on the dorsal and palmar surfaces. 

The interosseous ligaments (lujamenta hasium oss. metacarp. interossea) pass 
between their contiguous surfaces, just beneath their lateral articular facets. 



320 



THE ARTIGULA TIONS, OB JOINTS 



S3movial Membrane (Fig. 255). — ^The synovial membrane between the lateral facets is a 
reflection from that between the two rows of carpal bones. 




ANTERIOR 
>R VAGINAL 
LIGAMENT 

TRANSVERS 
METACARPAL 
kiGAMENT 



SECOND 
PALMAR 
MTER05SE0US 
MUSCLE 



Fig. 256. — Metacarpal bones and first phalanges of the second to the fifth finger of the right hand, with 
ligaments, from the volar surface. (Spaltebolz.) 



The transverse metacarpal ligament Qigamentum capitidorum oss. metacar- 
■paliuvi transversum) (Fig. 256) is a narrow, fibrous band which passes trans- 
Tersely across the anterior surfaces of the digital extremities of the four inner 
metacarpal bones, connecting them. It is blended anteriorly with the palmar 
ligaments of the metacarpophalangeal articulations. To its posterior border is 
connected the fascia which covers the Interossei muscles. Its anterior surface is 
concave where the Flexor tendons pass over it. Behind it the tendons of the 
Interossei muscles pass to their insertion. 



X. Metacarpophalangeal Articulations (ArticulationesMetacarpophalangeae) 

(Figs. 256, 257). 

These articulations are of the condyloid variety, formed by the reception of 
the rounded head of the metacarpal bone into a shallow cavity in the extremity 
of the first phalanx. The expansion of the Extensor communis digitorum tendoii 
acts as a dorsal ligament. There is a capsular ligament which at certain points 
has strengthening ligaments. The ligaments are: 



Anterior. 



Two Lateral. 



ARTICULATIONS OF THE PHALANGES 



321 



The palmar or vaginal ligament {li(/amentum vagmale, glenoid ligament of Cru- 
veilhier) is a thick, dense, fibrous structure, placed on the palmar surface of the 
joint in the interval between the lateral liga- 
ments, to which it is connected; it is loosely 
united to the metacarpal bone, but very firmly 
to the base of the first phalanx. Its palmar 
surface is intimately blended with the transverse 
metacarpal ligament, and presents a groove for 
the passage of the Flexor tendons, the sheath 
surrounding which is connected to each side of 
the groove. By its deep surface it forms part of 
the articular surface for the head of the meta- 
carpal bone, and is lined Ijy a synovial mem- 
brane. 

The lateral ligaments (Ucjamcnta coUateralia) 
are strong, rounded cords placed one on each side 
of the joint, each being attached by one extremity 
to the posterior tubercle on the side of the head 
of the metacarpal bone, and by the other to the ahticu 
contiguous extremity of the phalanx. 

Movements. — The movements which occur in these 
joints are flexion, extension, adduction, abduction, and 
circumduction; the lateral movements are very extensive. 

Surface Form. — The prominences of the knuckles do 
not correspond to the position of the joints either of the 
metacarpophalangeal or interphalangeal articulations. 
These prominences are invariably formed by the distal 
ends of the proximal bone of each joint, and the line 
indicating the position of the joint must be sought con- 
siderably in front of the middle of the knuckle. 




ARTICULAR 
CAPSULE 



XI. Articulations of the Phalanges (Articu- 
lationes Digitorum Manus) (Fig. 257) 

These are ginglymus joints. Each joint has a 
capsule, and certain accentuated portions are re- 
garded as definite ligaments. These ligaments 



Anterior or Palmar. 

Two Lateral {ligamenta coUateralia). 

The arrangement of these ligaments is similar 
to those in the metacarpophalangeal articula- 
tions; the Extensor tendon supplies the place 
of a dorsal ligament. 




Fig. 257. — Metacarpal bones and first 
phalanges of the third finger of the right 
nand. with ligaments, from the radial side, 
(Spalteholz.) 



Movements. — The only movements permitted in the phalangeal joints are flexion and 
extension; these movements are more extensive between the first and second phalanges than 
between the second and third. The movement of flexion is very considerable, but extension 
is limited by the anterior and lateral ligaments. 

•21 



322 THE ARTICULATIONS, OR JOINTS 



ARTICULATIONS OF THE LOWER EXTREMITY. 

The articulations of the lower extremity comprise the following groups: 



I. The Hip-joint. 
11. The Knee-joint. 
III. The Articulations between the 



VI. The Tarsometatarsal Articulations, 

VII. Articulations of the Metatarsal 

Bones with each other. 



Tibia and Fibula. I \^III. The Metatarsophalangeal Articu- 

IV. The Ankle-joint. i lations. 

V. The Articulations of the Tarsus, j IX. TheArticulations of the Phalanges. 



I. The Hip-joint (Articulatio Coxae) (Figs. 258, 2.59). 

This articulation is an enarthrodial or ball-and-socket joint, formed by the 
reception of the head of the femur into the cup-shaped cavity of the acetabulum. 
The articulating surfaces are covered by hyaline cartilage, that on the head of 
the femur being thicker at the centre than at the circumference, and covering 
the entire surface with the exception of a depression just below its centre for the 
attachment of the ligamentum teres; that covering the acetabulum is much thinner 
at the centre than at the circumference. This cartilage forms an incomplete 
ring of a horseshoe shape, being deficient below, where there is a circular depres- 
sion, which in the recent state is occupied by a mass of fat covered by synovial 
membrane. The ligaments of the joints are the 

Capsular. Teres. 

Iliofemoral. Cotyloid. 

Transverse. 

The capsular ligament (capsula articularis) (Figs. 258 and 259) is a strong, dense, 
ligamentous capsule, embracing the margin of the acetabulum above and surround- 
ing the neck of the femur below. Its upper circumference is attached to the acetab- 
ulum a short distance above and behind the cotyloid ligament, but in frotit it is 
attached to the outer margin of the ligament, and opposite to the notch, where 
the margin of this cavity is deficient, it is connected to the transverse ligament, 
and by a few fibres to the edge of the obturator foramen. Its loioer circumference 
surrounds the neck of the femur, being attached, in front, to the spiral or anterior 
intertrochanteric line; above, to the base of the neck; behind, to the neck of the 
lione, about half an inch above the posterior intertrochanteric line. From this 
insertion the fibres are reflected upward over the neck of the femur, forming a 
sort of tubular sheath, the cervical reflection, which blends with the periosteum 
and can be traced as far as the cartilage which covers the head of the femur. 
On the surface of the neck of the femur some of these reflected fibres are raised 
into longitudinal folds, termed retinacula. It is much thicker at the upper and 
fore part of the joint, where the greatest amount of resistance is required, than 
below and internally, where it is thin, loose, and longer than in any other part. 
It consists of two sets of fibres, circular and longitudinal. The circular fibres, 
zona orbicularis (Fig. 261), are most abundant at the lower and back part of the 
capsule, and form a sling or collar around the neck of the femur. Anteriorly 
they blend with the deep surface of the iliofemoral ligament, and through this 
medium reach the anterior inferior spine of the ilium. The longitudinal fibres 
are greatest in amount at the upper and front part of the capsule, where 



THE HIP-JOINT 



323 



they form distinct bands or accessory ligaments, of which the most important 
is the iliofemoral. Other accessory bands are iinown as the pubofemoral (Jiga- 
mentum pubocapsidare), passing from the outer portion of the horizontal pubic 
ramus, the iliopectineal eminence, the obturator crest and the obturator mem- 




M 




OFEMORAL 
1_ I G AM E ?MT 



ANTERIOR 

INTERTRO 

CHANTERIC LINE 




Fig. 258. — Right hip-joint, from in front. (Spalteholz.) 

brane, to the front of the capsule; and the ischiocapsular ligament or ligament 
of Bertin (ligamentum ischiocapsulare), which passes from the ischium, just laelow 
the acetabulum, to blend with the circular fibres at the lower part of the joint. 
The external surface is rough, covered by numerous muscles, and separated in 
front from the Psoas and Iliacus muscles by a synovial bursa, which not infre- 
quently communicates, by a circular aperture, with the cavity of the joint. It 
differs from the capsular ligament of the shoulder in being much less loose and 
lax, and in not being perforated for the passage of a tendon. 

The iliofemoral (ligamentum iliofemorale) (Figs. 261 and 262) is an accessory 
band of fibres extending obliquely across the front of the joint; it is intimately 
connected with the capsular ligament, and serves to strengthen it in this situa- 



324 



THE ARTICULATIONS, OB JOINTS 



tion. It is attached, above, to the lower part of the anterior inferior spine of the 
ihum and the adjacent rim of the acetabulum; and, diverging below, forms two 
bands, of which one passes downward to be inserted into the lower part of the 
anterior intertrochanteric line; the other passes downward and outward to be 
inserted into the upper part of the same line and the adjacent part of the neck 
of the femur. Between the two bands is a thinner part of the capsule. Some- 
times there is no division, but the ligament spreads out into a flat, triangular 







Fig. 259.— Right hip-joint, from behind. (The 



band, which is attached below into the whole length of the anterior intertrochan- 
teric line. This ligament is frequently called the Y-shaped ligament of Bigelow; 
and the outer or upper of the two bands is sometimes described as a separate 
ligament, under the name of the iliotrochanteric ligament. 

The ligamentiun teres {ligamentuin teres femoris) (Figs. 261 and 262) is a tri- 
angular band implanted by its apex into the depression a little behind and below 



THE HIP JOINT 



325 



the centre of the head of the femur, and by its broad base into the margins of the 
cotyloid notch, where it blends with the transverse ligament. It is formed of 
white fibrous connective tissue, surrounded by a tubular sheath of synovial mem- 
brane. Sometimes only the synovial fold exists. Very rarely it is absent. The 
ligament is made tense when the hip is semiflexed, and the limb adducted and 
rotated outward; it is, on the other hand, relaxed when the limb is abducted. 
It has, however^ but little influence as a ligament, and though it may to a certain 
extent limit movement, it would appear to be merely a "vestigial and practically 
useless ligament.'" 




Fig. 260. — Right hip-joint from the mesal side. (The bottom of the acetabulum has been chiselled away 
sufficiently to make the head of the femur visible.) (Spalteholz.) 



The cotyloid ligament {labruvi glenoidale (Fig. 263) is a fibrocartilaginous rim 
attached to the margin of the acetabulum, the cavity of which it deepens; at the 
same time it protects the edges of the bone and fills up the inequalities on its sur- 
face. It bridges over the notch as the transverse ligament of the acetabulum, and 
thus forms a complete circle, which closely surrounds the head of the femur, 
and assists in holding it in its place. It is prismoid on section, its base being 
attached to the margin of the acetabulum and its opposite edge being free and 
sharp. Its two surfaces are invested by synovial membrane, the external one being 
in contact with the capsular ligament, the internal one being inclined inward, so 
as to narrow the acetabulum and embrace the cartilaginous surface of the Tiead 
of the femur. It is much thicker above and behind than below and in front, 
and consists of close, compact fibres, which arise from different points of the 

1 J. Bland Sutton, Ligaments: Their Nature and Morphology, 1887. 



326 



THE ARTICULATIONS, OR JOINTS 



circumference of the acetabulum and interlace with each other at very acute 
angles. 

The transverse ligament of the acetabulum Qigamentum transversum acetahidi) 
(Figs. 260 and 263) is in reality a portion of the cotyloid hgament, though difFering 
from it in having no cartilage cells among its fibres. It consists of strongs 
flattened fibres, which cross the notch at the lower part of the acetabulum and 
convert it into a foramen. Thus an interval is left beneath the ligament for the 
passage of nutrient vessels to the joint. 



R LIGAMENT 



CAPSULA 

FIBRO 

CAPSULA 

SYNOV 




OPER'S LIGAMENT 
)F PUBIS 



Fig. 261. — The right hip-joint, seen from before. (Toldt.) 



The synovial membrane (Figs. 261 and 262) is very extensive. Commencing at the margin 
of the cartilaginous surface of the head of the femur, it covers all that portion of the neck which 
is contained within the joint; from the neck it is reflected on the internal surface of the capsular 
ligament; it covers both surfaces of the cotyloid ligament and the mass of fat contained in the 
depression at the bottom of the acetabulum, and it is prolonged as far as the head of the femur 
in the form of a tubular sheath around the ligamentum teres. It sometimes communicates 
through an aperture in the capsular ligament between the inner band of the Y-shaped ligament 
and the pubofemoral ligament with a bursa situated on the under surface of the Iliopsoas 
muscle. 

The muscles in relation with the joint (Fig. 263) are, in front, the Psoas and Iliacus, sepa- 
rated from the capsular ligament by a synovial bursa; above, the reflected head of the Rectus 
femoris and Gluteus minimus, the latter being closely adherentto the capsule; internally, the 



THE HIP-JOINT 



•i21 



Obturator externus and Pectineus; behind, the Pyriformis, Gemellus superior, Obturator 
internus, Gemellus inferior, Obturator externus, and Quadratus femoris. 

The arteries supplying the joint are derived from the obturator, sciatic, internal circumflex, 
and gluteal. 

The nerves are articular branches from the sacral plexus, great sciatic, obturator, accessory 
obturator, and a filament from the branch of the femoral (anterior crural) supplying the 
Rectus femoris. 

Bursas. — Numerous bursse exist in the neighborhood of the hip-joint. Some anatomists have 
counted twenty-one (Synnestredt). The chief ones are: (1) The iliopectineal bursa (bursa ilio- 
pcctinea) (Fig. 264), between the Iliopsoas tendon and the capsule of the joint. This bursa 
often communicates with the hip-joint. (2) The subtendinous iliac bursa (biirxa iliaca .lub- 
tendiiiea), between the tendon of the Psoas and Iliacus and the lesser trochanter. (3) The ischio- 




FiG. 262.— Right hip-joint. Frontul section. Posterior half, viewed from in front. The joint surfaces 
hiive been somewhat pulled apart. (Spalteholz.) 



gluteal bursa (bursa ischiadica m. glutaei maximi), between the Gluteus maximus muscle and 
the tuberosity of the ischium (not constant). (4) The bursa of the greater trochanter (bursa 
trochanierica m. glutaei maximi), between the greater trochanter and the Gluteus maximus muscle 
near the muscular insertion. (.5) Two or three gluteofemoral bursae (bursae (/lufaiofimornles) 
below. (6) The obturator bursa (bursa m. ohtiirattu-ii iiilrnii), between the margin of the great 
sacrosciatic notch and the tendon of the Obturatdv internus muscle. (7) The subcutaneous 
trochanteric bursa (bursa trochanterica subcutanea), between the cutaneous surface and the great 



328 



THE ARTICULATIONS, OB JOINTS 



trochanter. Besides these there is a bursa between the greater trochanter and the anterior part 
of the Gluteus medius; between the greater trochanter and the posterior part of the Gluteus 
medius; between the greater trochanter and the Gluteus minimus; beneath the PjTiformis 
muscle; between the lesser trochanter and the Quadratus femoris muscle; and there are bursse 
beneath the Biceps femoris muscle. 

Movements. — The movements of the hip are very extensive, and consist of flexion, exten- 
s-ion, adducfion, abduction, circumduction, and rotation. 

The hip-joint presents a very striking contrast to the shoulder-joint in the much more com- 
plete mechanical arrangements for its security and for the limitation of its movements. In the 
shoulder, as we have seen, the head of the humerus is not adapted at all in size to the glenoid 
cavity, and is hardly restrained in any of its ordinary movements by the capsular ligament. In 
the hip-joint, on the contrary, the head of the femur is closely fitted to the acetabulum for a 
distance extending over nearly half a sphere, and at the margin of the bony cup it is still more 
closely embraced by the cotyloid ligament, so that the head of the femur is held in its place by 
that ligament even when the fibres of the capsule have been cjuite divided (Humphry). The 
anterior portion of the capsule, described as the iliofemoral ligament, is the strongest of all 
the ligaments in the body, and is put on the stretch by any attempt to extend the femur 
beyond a straight line with the trunk. That is to say, this ligament is the chief agent in main- 
taining the erect position without muscular fatigue; for a vertical line passing through the 




Fig. 263. — Relation oi ii i U t , t le capsule of the hip-joint. (From a drawing by Mr. F. A. Barton.) 

centre of gravity of the trunk falls behind the centres of rotation in the hip-joint, and therefore 
the pelvis tends to fall backward, but is prevented by the tension of the iliofemoral and capsular 
ligaments. The security of the joint may be also provided for by the two bones being directly 
united through the ligamentum teres; but it is doubtful whether this so-called ligament can have 
much influence upon the mechanism of the joint. Flexion of the hip-joint is arrested by the 
soft parts of the thigh and abdomen being brought into contact when the leg is flexed on the 
thigh ; and by the action of the Hamstring muscles when the leg is extended.' Extension is 
arrested by the tension of the iliofemoral ligament and the front of the capsule; adduction, 
by the thighs coming into contact; adduction loith flexion, by the outer band of the iliofemoral 
ligament, and the outer part of the capsular ligament; abduction, by the inner band of the ilio- 



• The hip-joint cannot be completely fieved, in most persons, without at the same time flexing the knee, on 
account of the shortness of the Hamstring muscles. — Cleland, Jour, of Anat. and Physiol, No. l.Old Series, p. 87. 



THE HIP-JOINT 



329 



femoral ligament and the pubofemoral band ; rotation outward, by the outer band of the iliofemoral 
ligament; and rotation inward, by the isehiocapsular ligament and the hinder part of the cap- 
sule. The muscles which flex the femur on the pelvis are the Psoas, Iliacus, Rectus femoris, 
Sartorius, Pectineus, Adductor longus and brevis, and the anterior fibres of the Gluteus medius 
and minimus. Extension is mainly performed by the Gluteus maximus, assisted by the Ham- 
string muscles. The thigh is atlducted by the Adductores magnus, longus, and brevis, the 
Pectineus, the Gracilis, and the lower part oi' the Gluteus maximus, and abducted by the Gluteus 
medius and minimus and the upper part of the Gluteus maximus. The muscles which rotate 
the thio-h inward are the anterior fibres of the Gluteus medius, the Gluteus minimus, and 
the Tensor fasciae femoris; while those which rotate it outward are the posterior fibres of the 
<iluteus medius, the Pyriformis, Obturator externus and internus, Gemellus superior and inferior, 
Quadratus femoris, Iliacus, Gluteus maximus, the three Adductors, the Pectineus, and the 
Sartorius. 

Surface Form. — A line drawn from the anterior superior spinous process of the ilium to 
the most prominent part of the tuberosity of the ischium (Nelaton's line) runs through the 
centre of the acetabulum, and would, therefore, indicate the level of the hip-joint; or, in other 
words, the upper border of the great trochanter, which lies on Nekton's line, is on a level with 
the centre of the hip-joint. 

Applied Anatomy. — Inflammation of hursoB about the hip-joint gives rise to confusing 
symptoms, and is not uncoriimonly mistaken for hip-joint disease. 



Great sacrosciat 



Small sacrosctatic 
ligament 




' J Anterior superior 
spine 



.Great trochanter 
of femur. 



Fig. 264. — Nelaton's line and Bryant's triangle. 



In dislocation of the hip "the head of the thigh bone may rest at any point around its socket" 
(Bryant); but whatever position the head ultimately assumes, the primary displacement is 
generally downward and inward, the capsule giving way at its weakest — that is, its lower and 
inner — part. The situation that the head of the bone subsequently assumes is determined 
by the degree of flexion or extension, and of outward ov inward rotation of the thigh at the 
moment of luxation, influenced, no doubt, by the iliofemoral ligament, which is not easily rup- 
tured. When, for instance, the head is forced backward, this ligament forms a fixed axis, around 
which the head of the bone rotates, and the head is thus driven on to the dorsum of the ilium. 
The iliofemoral ligament also influences the position of the thigh in the various dislocations: 
in the dislocations backward it is tense, and produces inversion of the limb; in the dislocation 
on to the pubes it is relaxed, and therefore allows the External rotators to evert the thigh; while 
in the thyroid dislocation it is tense and produces flexion. 



330 THE ABTICULA TIONS, OB JOINTS 

. The iliofemoral ligament is rarely torn in dislocations of the hip, and this fact is taken advan- 
tao-e of by the surgeon in reducing these dislocations by manipulation. It is made to act as 
a fulcrum to a lever of which the long arm is the shaft of the femur, and the short arm the 
neck of the bone. 

The hip-joint is rarely the seat of acute synovitis from injury, on account of its deep position 
and its thick covering of soft parts. Acute inflammation may, and does, frequently occur as 
the result of constitutional conditions, as rheumatism, pyemia, etc. When, in these cases, 
effusion takes place, and the joint becomes distended with fluid, the swelling is not very easy 
to detect on account of the thickness of the capsule and the depth of the articulation. It is 
principally to be found on the front of the joint, just internal to the iliofemoral ligament; or 
behind, at the lower and back part. In these two places the capsule is thinner than elsewhere. 
Disease of the hip-joint is much more frequently of a chronic character and is usually, of tuber- 
culous origin. It begins either in the bones or in the synovial membrane, more frequently in the 
former, and probably, in most cases, in the growing, highly vascular tissue in the neighborhood 
of the epiphyseal cartilage. In this respect it differs very materially from the tuberculous arthritis 
of the knee, where the disease often commences in the synovial membrane. 

In chronic hip disease the affected limb assumes an altered position, the cause of which it 
is important to understand. In the early stage of a typical case the limb is flexed, abducted, 
and rotated outward. In this position all the ligaments of the joint are relaxed — the front of 
the capsule by flexion; the outer band of the iliofemoral ligament by abduction; and the inner 
band of this ligament and the back of the capsule by rotation outward. It is, therefore, the 
position of the greatest ease. The condition is not quite obvious at first upon examining a 
patient. If the patient is laid in the supine position, the affected limb will be found to be ex- 
tended and parallel with the other. But it will be found that the pelvis is tilted downward on 
the diseased side and the limb apparently longer than its fellow, and that the lumbar portion of 
the vertebral column is arched forward (lordosis). If now the thigh is abducted and flexed, the tilt- 
ino- downward and the arching forward of the pelvis disappears. The condition is thus explained. 
A limb which is flexed and abducted is obviously useless for progression, and, to overcome the 
difficulty, the patient depresses the affected side of his pelvis in order to produce parallelism 
of his limbs, and at the same time rotates his pelvis on its transverse horizontal axis, so as to 
direct the limb downward instead of forward. In the latter stages of the disease the limb becomes 
flexed, adducted, and inverted. The position probably depends upon the muscular action, 
at all events as regards the adduction. The Adductor muscles are supplied by the obturator 
nerve, which also largely supplies the joint. These muscles are therefore thrown into reflex 
a?tion by the irritation of the peripheral terminations of this nerve in the inflamed articulation. 
Osteoarthritis is not uncommon in the hip-joint, and it is said to be more common in the male 
than in the female, in whom the knee-joint is more frequently affected. It is a disease of middle 
age or more advanced period of life. 

Congenital dislocation is more commonly met with in the hip-joint than in any other articula- 
tion. The displacement usually takes place on to the dorsum ilii. It gives rise to extreme 
lordosis, and a waddling gait is noticed as soon as the child commences to walk. 

Excision of the hip may be required for disease or for injury, especially for gunshot wound. 
It may be performed either by an anterior or an external incision. The former one entails 
less interference with important structures, especially muscles, than the posterior one, but . 
permits of less efficient drainage. In the operation in front the surgeon makes an incision 
three or four inches in length, starting immediately below and external to the anterior superior 
spinous process of the ilium, downward and inward between the Sartorius and Tensor fasciae 
femoris, to the neck of the bone, dividing the capsule at its upper part. A narrow-bladed saw 
now divides the neck of the femur, and the head of the bone is extracted with sequestrum forceps. 
All diseased tissue is carefully removed with a sharp spoon or scissors, and the cavity thoroughly 
flushed with a hot aseptic fluid. 

The external method consists in making an incision three or four inches long, commencing 
midway between the top of the great trochanter and the anterior superior spine, and ending 
over the shaft, just below the trochanter. The muscles are detached from the great trochanter, 
and the capsule opened freely. The head and neck are freed from the soft parts and the bone 
sawed through just below the top of the trochanter with a narrow saw. The head of the bone is 
then levered out of the acetabulum. In both operations, if the acetabulum is eroded, it must be 
freely gouged. 



THE KNEE-JOINT 331 



II. The Knee-joint (Articulatio Genu). 

The knee-joint was formerly described as a ginglymus or hinge-joint, but is 
really of a much more complicated character. It must be regarded as consist- 
ing of three articulations in one — one between each condyle of the femur and the 
corresponding tuberosity of the tibia, which are condyloid joints, and one between 
the patella and the femur, which is partly arthroidal, but not completely so, since 
the articular surfaces are not mutually adapted to each other, so that the movement 
is not a simple gliding one. This view of the construction of the knee-joint 
receives confirmation from the study of the articulation in some of the lower 
mammals, where three synovial membranes are sometimes found, corresponding 
to these three subdivisions, either entirely distinct or only connected by small 
communications. This view is further rendered probable by the existence of 
the two crucial ligaments within the joint, which must be regarded as the external 
and internal lateral ligaments of the inner and outer joints respectively. The 
existence of the ligamentum mucosum would further indicate a tendency to sepa- 
ration of the synovial cavity into two minor sacs, one corresponding to each joint. 

The bones entering into the formation of the knee-joint are the condyles of the 
femur above, the head of the tibia beloiv, and the patella in front. The bones are 
connected by ligaments, some of which are placed on the exterior of the joint, 
while others occupy its interior. 

External Ligaments. Interior Ligaments. 

Capsular. Anterior, or External Crucial. 

Anterior, or Ligamentum Patellae. Posterior, or Internal Crucial. 

Posterior. Two Semilunar Fibrocartilages. 

Internal Lateral. Transverse. 

Two External Lateral. Coronary. 

The capsular ligament (capsula articularis) (Fig. 265) consists of an exceedingly 
thin, but strong, fibrous membrane, which is strengthened in almost its entire 
extent by heavy bands which are inseparably connected with it. In front it blends 
with and forms part of the lateral patellar ligaments and fills in the interval 
between the anterior and lateral ligaments of the joints, with which latter structures 
it is closely connected. It is deficient above the joint and beneath the tendon of 
the Quadriceps extensor. Behind, it is formed chiefly of vertical fibres, which 
arise above from the condyles and intercondyloid notch of the femur, and is con- 
nected below with the back part of the head of the tibia, being closely united 
with the origins of the Gastrocnemius, Plantaris, and Popliteus muscles. It 
passes in front of, but is inseparably connected with, the posterior ligament. 

The anterior ligament, or ligamentimi patellae (Figs. 265, 269, and 270), is the 
central portion of the common tendon of the Extensor muscles of the thigh, which 
is continued from the patella to the tubercle of the tibia, supplying the place of 
an anterior ligament. It is a strong, flat, ligamentous band about three inches in 
length, attached, above, to the apex of the patella and to the rough depression on 
its posterior surface; below, to the lower part of the tubercle of the tibia, its super- 
ficial fibres being continuous over the front of the patella with those of the tendon 
of the Quadriceps extensor. The lateral portions of the tendon of the Extensor 
muscles in conjunction with the fascia lata pass down on either side of the patella, 
and are attached to the tibia on either side of the tubercle; these are termed 
lateral patellar ligaments (retinaculum patellae mediale et laterale), and merge 
into the capsule. The posterior surface of the ligamentum patellae is separated. 



332 



THE ARTICULATIONS, OB, JOINTS 



above, from the synovial membrane by a fold of fat; beloiv, it is separated from 
the head of the tibia by a synovial bursa. 

The posterior ligament {ligamentum popliteum ohliquum) (Fig. 266) is a broad, 
flat, fibrous band, formed of fasciculi separated from one another by apertures 
for the passage of vessels and nerves. It is attached, above, to the upper margin 
of the intercondyloid notch of the femur, and, below, to the posterior margin of 
the head of the tibia. Superficial to the main part of the ligament and forming 
a portion of it is a strong fasciculus derived from the tendon of the Semimembra- 
nosus; it passes from the back part of the inner tuberosity of the tibia obliquely 
upward and outward to the back part of the outer condyle of the femur and blends 
with the posterior ligament. This expansion from the tendon of the Semimem- 





FiG 265 — Right knee joint Anterior 



Fig. 266. — Right knee-joint. Posterior ■ 



branosus muscle is called the posterior ligament of Winslow. The posterior liga- 
ment forms part of the floor of the popliteal space, and the popliteal artery rests 
upon it. 

The internal lateral ligament {ligamentum collaterale tibiale) (Figs. 265 and 
266) is a broad, flat, membranous band, thicker behind than in front, and situated 
nearer to the back than the front of the joint. It is attached, above, to the inner 
tuberosity of the femur; below, to the inner tuberosity and inner surface of the 
shaft of the tibia to the extent of about two inches. It is crossed, at its lower 
part, by the tendons of the Sartorius, Gracilis, and Semitendinosus muscles, a 
synovial bursa being interposed. Its deef surface covers the anterior portion of 
the tendon of the Semimembranosus, with which it is connected by a few fibres, 
and the inferior internal articular vessels and nerve; it is intimately adherent 
to the internal semilunar fibrocartiiage. 



THE KNEE-JOINT 



333 



Femur. 



The external lateral or long external lateral ligament (Ugamentum collaierale 

fibidare) (Figs. 266 and 270) is a .strong, rounded, fibrous cord situated nearer 

to the back than the front of the joint. It is attached, above, to the back part 

of the outer tuberosity of the femur; below, 

to the outer part of the head of the fibula. 

Its outer surface is covered by the tendon 

of the Biceps femoris, which divides at its 

insertion into two parts, separated by the 

ligament. The ligament has, passing be- 
neath it, the tendon of the Popliteus muscle 

and the inferior external articular vessels 

and nerve. 
The short external lateral ligament 

(ligamentum laterale externum breve seu 

posticum) (Fig. 266) is not a constant 

structure. It is an accessory bundle of 

fibres placed behind and parallel with the 

preceding, attached, above, to the lower 

and back part of the outer tuberosity of the 

femur; below, to the summit of the styloid 

process of the fibula. This ligament is in- 
timately connected with the capsular liga- 
ment, and has, passing beneath it, the 

tendon of the Popliteus muscle and the 

inferior external articular vessels and nerve. 
The crucial ligaments (ligamenta cru- 

ciata genu) (Figs. 267 and 268) are two 

interosseous ligaments of considerable 

strength situated in the interior of the joint, 

nearer its posterior than its anterior part. 

They are called crucial because they cross 

each other somewhat like the lines of the 

letter X; and have received the names anterior crucial and posterior crucial, from 

the position of their attachment to the tibia. 

The anterior or external crucial ligament {ligamentum cruciatum anterhis) (Fig. 

267) is attached to the depression in front of the spine of the tibia, being blended 

with the anterior extremity 
of the external semilunar 
fibrocartilage, and, passing 
obliquely upward, backward, 
and outward, is inserted into 
the inner and back part of 
the outer condyle of the 
femur. 

The posterior or internal 
crucial ligament {ligamen- 
tum cruciatum posterius) is 
stronger, but shorter and 
less oblique in its direction 
than the anterior. It is at- 
tached to the back part of 
the depression behind the 

spine of the tibia, to the popliteal notch, and to the posterior extremity of the 

external semilunar fibrocartilage; and passes upward, forward, and inward, to 




Showing interior 




Fig. 268.— Head of tibi 



milunir oirtil iges 
Right side. 



334 



THE ARTICULATIONS, OR JOINTS 



be inserted into the outer and fore part of the Inner condyle of the femur. It is 
in relation, in front, with the anterior crucial ligament; behind, with the capsular 
ligament. 

The semilunar fibrocartilages (menisci) (Figs. 267 and 268) are two crescentic 
lamellfe which serve to deepen the surface of the head of the tibia, for articula- 
tion with the condyles of the femur. The circumference of each cartilage is thick, 
convex, and attached to the inside of the capsule of the knee; the inner border 




PATELLAR BURSA 



TUBEROSITY 



.t.-l'^'fiy" "^,1.%* J.'^tVtJ'HV'' 1 O'' TIBIA 
^ . ' v/ -'. &* * V * -e a » -^ V S 







Fig. 269. — Right knee-ioint Sagittal section through the external condyle of the femur. Mesal half oi 
section, from the lateral side. The knee is slightly flexed; the joint surfaces have been pulled a little apart. 
<Spalteholz.) 

is thin, concave, and free. Their upper surfaces are concave, and in relation 
with the condyles of the femur; their lower surfaces are flat, and rest upon the 
head of the tibia. Each cartilage covers nearly the outer two-thirds of the 
corresponding articular surface of the tibia, leaving the inner third uncovered; 
both surfaces are smooth and invested by synovial membrane. 

The internal semilunar fibrocartilage {tiieniscus medialis) is nearly semicir- 
cular in form, a little elongated from before backward, and broader behind than 



THi: KNEE-JOINT 



335 



in front; its anterior extremity, thin and pointed, is attached to a depression on the 
anterior margin of the head of the tibia, in front of the anterior crucial Hgament; 
its posterior extremity is attached to the depression behind the spine, between 
the attachments of the external cartilage and the posterior crucial ligaments. 

The external semilunar fibrocartilage {meniscus lateralis) forms nearly an entire 
circle, covering a larger portion of the articular surface than the internal one. 



J OF QUAD- 
RICEPS EXTENSOR 
FEMORIS 




13MG EXTE 

LATERAL. 
LIGAMENT 



REPATELLAR 



TERNAL SEMI- 
NAR FIBRO- 
RTiLAGE 



FiQ. 270.— Eight knee-joint, from the lateral surface. The joint cavity and several bursffi have been injectea 
with a stiffening medium and then dissected out. (Spalteholz.) 



It is grooved on its outer side for the tendon of the Popliteus muscle. Its ex- 
tremities, at their insertion, are interposed between the two extremities of the 
internal cartilage; the anterior extremity is attached in front of the spine of the 
tibia to the outer side of, and behind, the anterior crucial ligament, with which 
it blends; the posterior extremity is attached behind the spine of the tibia, in 
front of the posterior extremity of the internal cartilage. Just before its insertion 



336 THE ARTICULATIONS, OH JOINTS 

posteriorly it gives off a strong fasciculus, tlie ligament of Wrisberg, which passes 
obliquely upward and outward, to be inserted into the inner condyle of the femur, 
close to the attachment of the posterior crucial ligament. Occasionally a small 
fasciculus is given off which passes forward to be inserted into the back part 
of the anterior crucial ligament. The external cartilage gives oft' from its anterior 
convex margin a fasciculus which forms the transverse ligament. 

The transverse ligament (ligamentum transversum genu) (Fig. 268) is a 
band of fibres which passes transversely from the an